Semiconductor laser element

ABSTRACT

To provide a semiconductor laser device which has no ripple and can afford better FFP having a pattern near a Gaussian distribution upon operation at the high output, the semiconductor laser comprising a laminate structure in which a first conductive type semiconductor layer, an active layer and a second conductive type semiconductor layer different from the first conductive type are laminated in this order, the laminate structure having a waveguide region to guide a light and resonator planes for laser oscillation on both ends, characterized in that the laminate structure has a non-resonator plane on one end side and the non-resonator plane is covered with a shading layer.

TECHNICAL FIELD

[0001] The present invention relates to a semiconductor laser devicehaving the better far field pattern (FFP), more particularly, it relatesto a semiconductor laser device using a III-V Group nitridesemiconductor comprising GaN, AlN or InN, or a mixed crystal thereof(In_(x)Al_(y)Ga_(1−x−y)N, 0≦x, 0≦y, x+y≦1).

BACKGROUND ART

[0002] Recently, a semiconductor laser device has progressed inminiaturization, lightening, high reliance and high output and, thus, isutilized as a light source for personal computers, electronic equipmentsuch as DVD, processing equipment and optical fiber communication. Interalia, a nitride semiconductor (In_(x)Al_(y)Ga_(1−x−y)N, 0≦x, 0≦y, x+y≦1)attracts attention as a semiconductor laser device which can emit from arelatively short wavelength ultraviolet region to a red color.

[0003] In such the semiconductor laser device, a buffer layer, an n-typecontact layer, a crack-preventing layer, an n-type cladding layer, ann-type light-guiding layer, an active layer, p-type cap layer, a p-typelight-guiding layer, a p-type cladding layer and a p-type contact layerare formed in this order on a sapphire substrate. In addition, astripe-like emitting layer is formed by etching or the like and, then, ap-side electrode and an n-side electrode are formed. Further, after alight emitting plane is formed at a prescribed resonator length, amirror plane on a light reflecting side is formed, whereby, theoscillated light can be effectively taken out through the mirror plane.

[0004] However, in such the structure, there is a problem thatirregularity (ripple) is generated in far field pattern (FFP), leadingto a non-Gaussian distribution. In a semiconductor laser device in whichFFP has a non-Gaussian distribution, there is also a problem thatcalculation of a shape of FFP makes a great error, and connection to anoptical system can not be realized effectively and, for this reason, adriving current becomes great.

[0005] In addition, in the previous semiconductor laser device, there isa problem that an emitting end is easily deteriorated.

[0006] Then, the first object of the present invention is to provide asemiconductor laser device which has no ripple and can afford better FFPhaving a pattern near a Gaussian distribution upon operation at the highoutput.

[0007] In addition, the second object of the present invention is toprovide a semiconductor laser device which can prevent an end fromdeteriorating and afford better FFP even when operated at the highoutput.

DISCLOSURE OF THE INVENTION

[0008] In order to solve the aforementioned problems, the firstsemiconductor laser device of the present invention includes a laminatestructure in which a first conductive type semiconductor layer, anactive layer and a second conductive type semiconductor layer differentfrom the first conductive type are laminated in this order. The laminatestructure has a waveguide region to guide a light in one direction andresonator planes for laser oscillation on both ends. The firstsemiconductor laser device is characterized in that said laminatestructure has a non-resonator plane which is different from theresonator plane on one end side. The non-resonator plain is formed so asto contain a cross-section of the active layer and the cross-section ofsaid active layer of the non-resonator plane is covered with a shadinglayer.

[0009] By adopting such a structure, release of the light exuded from awaveguide region (stray light) from the non-resonator plane to theoutside is blocked to prevent from being overlapped with a main beamemitted from a resonator plane (that is, only a main beam can beemitted, and a ripple is prevented from generating) and, thus, excellentFFP can be obtained.

[0010] In addition, it is preferable that the resonator plane isprojected more than the non-resonator plane in the first semiconductorlaser device of the present invention, whereby, stray light can beeffectively prevented from releasing to the outside. In addition, bydoing so, the light emitted from the resonator plane is not blocked bythe non-resonator plane.

[0011] Further, in the first semiconductor laser device of the presentinvention, by adopting a resonator plane formed, in the vicinity ofwhich a non-resonator plane is formed, as an emitting plane for thelaser light, more excellent FFP can be obtained.

[0012] In addition, the second semiconductor laser device of the presentinvention includes a laminate structure in which a first conductive typesemiconductor layer, an active layer and a second conductive typesemiconductor layer different from the first conductive type arelaminated in this order. The laminate structure has a waveguide regionto guide a light in one direction and resonator planes for laseroscillation on both ends. In the second semiconductor laser device, aside of the laminate structure has a first side containing across-section of the active layer, and a second side which is situatednearer the waveguide region than the first side and contains across-section of the active layer, and a shading layer is provided onthe cross-section of the active layer of the second side.

[0013] The thus structured second semiconductor laser device of thepresent invention can block stray light released from a side of anactive layer to the outside at a position nearer a waveguide region.

[0014] In addition, in the second semiconductor laser device of thepresent invention, by provision of such the second side of the vicinityof a light emitting-plane, stray light can be effectively blocked and,thus, excellent FFP can be obtained.

[0015] In addition, the third semiconductor laser device of the presentinvention includes a laminate structure in which a first conductive typesemiconductor layer, an active layer and a second conductive typesemiconductor layer different from the first conductive type arelaminated in this order. The laminate structure has a waveguide regionto guide a light in one direction and resonator planes for laseroscillation on both ends. The third semiconductor laser devicecharacterized in followings.

[0016] (1) The laminate structure has a non-resonator plane which isdifferent from said resonator plane and the non-resonator plain isformed so as to contain a cross-section of said active layer.

[0017] (2) The side of the laminate structure has a first sidecontaining a cross-section of the active layer and a second side whichis situated nearer the waveguide region than the first side and near theemitting plane, and which contains a cross-section of an active layer.

[0018] (3) The shading layer is provided on the cross-section of theactive layer of at least one of the non-resonator plane and the secondside.

[0019] Herein, the shading layer may be provided on a non-resonatorplane or a second side, or on both of them. Thereby, stray light from anend side and stray light from a side can be blocked.

[0020] In addition, a structure in which this non-resonator plane and asecond side are directly connected is preferable. Further, it ispreferable that a shading layer is provided on both of the non-resonatorplane and the second side directly connected.

[0021] In addition, in the first to third semiconductor laser devices ofthe present invention, a stripe-like waveguide region can be formed byforming a stripe-like convex part. Thereby, a refractive index typewaveguide region can be structured, leading to a semiconductor laserdevice having the excellent device properties.

[0022] In addition, a shading layer of the present semiconductor laserdevice may be formed in contact with a laminate structure. Thereby,release of stray light exuded from a waveguide region to the outside canbe effectively blocked.

[0023] In addition, a shading layer of the present semiconductor laserdevice may be formed on an insulating layer provided on a laminatestructure. Thereby, a shading layer may be structured by using amaterial which is easily diffused into a device upon heat treatment.

[0024] In addition, as a shading layer of the present semiconductorlaser device, a layer comprising any of a conductor, a semiconductor andan insulator may be used. Thereby, the shading layer may be applied tolaminate structures made of various materials.

[0025] In addition, in a shading layer of the present semiconductorlaser device, a dielectric multi-layered membrane may be used. Thereby,stray light can be effectively blocked.

[0026] In addition, the present semiconductor laser device can bestructured by using a nitride semiconductor in a first conductive typesemiconductor layer, an active layer, and a second conductive typesemiconductor layer. With this structure, a semiconductor laser devicecan be obtained which is excellent in the durability and the safety andhas a wide range of wavelength from an ultraviolet region to a visibleregion.

[0027] In addition, the present semiconductor laser device ischaracterized in that a first conductive type semiconductor layer has ann-type nitride semiconductor and the second conductive typesemiconductor layer has a p-type nitride semiconductor.

[0028] In addition, in the present semiconductor laser device, it ispreferable that a shading layer is at least Ti and the insulating layeris SiO₂. Thereby, a layer through which the light is difficult totransmit and which reflects less light can be easily formed.

[0029] In addition, in the present semiconductor laser device, it ispreferable that a shading layer has at least an Rh oxide. Thereby, ashading layer through which the light is difficult to transmit and whichis stable can be formed.

[0030] In addition, in the present semiconductor laser device, a shadinglayer may be a multi-layered membrane composed of layers which comprisethe same material and have a different constitutional ratio. Thereby,layers of the same material but having the different membranous propertycan be formed.

[0031] The fourth semiconductor laser device of the present inventionincludes a laminate structure in which a first conductive typesemiconductor layer, an active layer and a second conductive typesemiconductor layer different from the first conductive type arelaminated in this order. The laminate structure has a waveguide regionto guide a light in one direction. The fourth semiconductor laser deviceis characterized in that the laminate structure has a shading membraneprovided in the vicinity of an emitting part of one end and at least onelayer of a light transmittable membrane comprising the same elements asthose constituting the shading membrane and having the highertransmittance than that of a shading membrane And the lighttransmittable membrane is provided between the shading membrane and thelaminate structure.

[0032] In the thus structured fourth semiconductor laser device of thepresent invention, a shading membrane which can control transmittance ofthe light can be provided tightly in the vicinity of a resonator plane.

[0033] In the fourth semiconductor laser device of the presentinvention, it is preferable that a shading membrane and a lighttransmittable membrane contain at least an Rh oxide.

[0034] The fifth semiconductor laser device of the present inventionincludes a laminate structure in which a first conductive typesemiconductor layer, an active layer and a second conductive typesemiconductor layer different from the first conductive type arelaminated in this order. The laminate structure has a waveguide regionto guide a light in one direction. The fifth semiconductor laser deviceis characterized in that said laminate structure has a protectivemembrane on at least one end face which has a first protective membraneand a second protective membrane having the lower light transmittancethan that of the first protective membrane.

[0035] By adopting such the structure, since the light emitted from anend can be controlled by a protective membranes having a difference inthe transmittance, a main beam can be prevented from being mixed withthe light other than a main beam and thus, better FFP can be obtained.

[0036] That is, in the fifth semiconductor laser device of the presentinvention, release of the light controlled by provision on an end of twoprotective membranes which are different at least in the lighttransmittance, it enables the laser light to be easily released from theresonator plane and it enables stray light to be released from thevicinity of a resonator plane with difficulty and, therefore, asemiconductor laser device can be obtained which has better FFP of thehigh output having no ripple and having a distribution near a Gaussiandistribution.

[0037] In addition, in the fifth semiconductor laser device of thepresent invention, it is preferable that the first protective membraneis provided on an emitting part of a resonator plane on an emittingside, and the second protective membrane is provided in the vicinity ofthe emitting part. Whereby, since the laser light (main beam) can beemitted effectively from the emitting part and, at the same time, thelight can be prevented form being released from the vicinity of theemitting part, better FFP is obtained. In addition, protection of anemitting part of a resonator plane with the first protective membranecan prevent COD from occurring.

[0038] In addition, in the fifth semiconductor laser device of thepresent invention, both of the first protective membrane and the secondprotective membrane are formed on the same end. Thereby, it becomespossible to control the light in a transverse direction relative to amain beam.

[0039] In addition, in the fifth semiconductor laser device of thepresent invention, an emitting plane may be formed so as to beprojected. By doing so, release of the light from the vicinity of anemitting part (plane) can be prevented, it becomes possible for thelight from the vicinity of the emitting part (plane) to be mixed withthe laser light released from an emitting part with difficulty and,thus, better FFP can be easily obtained. In addition, projection of aresonator plane can alter the diverging properties of the laser light.

[0040] In addition, in fifth semiconductor laser device of the presentinvention, the first protective membrane can be structured by asingle-layered or a multi-layered membrane of at least one selected fromcompounds such as oxides, nitrides and fluorides of Si, Mg, Al, Hf, Nb,Zr, Sc, Ta, Ga, Zn, Y, B and Ti. By using these materials, a protectivemembrane having the high transmittance can be obtained.

[0041] In addition, in the fifth semiconductor laser device of thepresent invention, the first protective membrane is a reflectionreducing coating (AR membrane (Anti-Reflection Coat)). Thereby,reflection of the light can be suppressed, and the laser light can beeffectively emitted.

[0042] In addition, in the fifth semiconductor laser device of thepresent invention, the first protective membrane having a refractiveindex which is within ±10% of that of a laminate structure ispreferable. Thereby, a device can be protected without altering theproperties of the light from an active layer.

[0043] In addition, in the fifth semiconductor laser device of thepresent invention, it is preferable that the second protective membraneis a shading membrane. This allows the light not to be released to theoutside from a part on which the second protective membrane is provided.

[0044] In addition, in the fifth semiconductor laser device of thepresent invention, it is particularly preferable that the firstprotective membrane is Nb₂O₅ and the second protective membrane is ashading membrane.

[0045] In addition, in the fifth semiconductor laser device of thepresent invention, a nitride semiconductor is used in a first conductivetype semiconductor layer, an active layer, and a second conductive typesemiconductor layer. In particular, it is preferable that a firstconductive type semiconductor layer has an n-type nitride semiconductor,and a second conductive type semiconductor layer has a p-type nitridesemiconductor. Thereby, a semiconductor laser device can be obtainedwhich has a wide emitting wavelength from the visible light to theultraviolet light.

BRIEF DESCRIPTION OF THE DRAWINGS

[0046]FIG. 1 is a perspective view of an external shape of asemiconductor laser device of an embodiment 1 of the present invention.

[0047]FIG. 2 is a cross-sectional view along the II-II line in FIG. 1.

[0048]FIG. 2 is a cross-sectional view along the III-III line in FIG. 1.

[0049]FIG. 4 is a perspective view a shape of a shading layer in asemiconductor laser device of an embodiment 1.

[0050] FIGS. 5 to 8 are a perspective view of a semiconductor laserdevice which is an alteration example of an embodiment 1.

[0051]FIG. 9 is a cross-sectional view of a semiconductor laser devicewhich is another alteration example in which an emitting end has a shapedifferent from that of FIG. 1 in an embodiment 1.

[0052]FIG. 10 is a cross-sectional view of a semiconductor laser deviceof another alteration example in which an emitting end has a shapedifferent from that of FIG. 9 in an embodiment 1.

[0053]FIG. 11 is a cross-sectional view of a semiconductor laser deviceof an example 4 of the present invention.

[0054]FIG. 12 is a perspective view of a semiconductor laser device ofthe example 4.

[0055]FIG. 13A is a perspective view of a semiconductor laser device ofan example 9 of the present invention.

[0056]FIG. 13B is a cross-sectional view along the XIIIB-XIIIB line inFIG. 13A.

[0057]FIG. 13C is a cross-sectional view along the XIIIC-XIIIC line inFIG. 13A.

[0058]FIG. 14A is a perspective view of a semiconductor laser device ofan embodiment 3 of the present invention.

[0059]FIG. 14B is a perspective view of the first and second protectivemembranes in an embodiment 3.

[0060]FIG. 14C is a cross-sectional view along the XIVC-XIVC line inFIG. 14A.

[0061]FIG. 15 is a perspective view of a semiconductor laser devicewhich is an alteration example in an embodiment 3.

[0062]FIG. 16 is a perspective view of a semiconductor laser devicewhich is another alteration example in an embodiment 3.

[0063]FIG. 17A, FIG. 17B, FIG. 18A, FIG. 18B are perspective views of asemiconductor laser device in an embodiment 4 of the present invention.

[0064]FIG. 19A is a graph showing a refractive index distribution and anelectric field intensity distribution in the case where a firstprotective membrane in not formed on an emitting plane, which graph isshown for comparing with a semiconductor laser device of an embodiment4.

[0065]FIG. 19B is a graph showing a refractive index distribution and anelectric field intensity distribution in the case where a firstprotective membrane comprising Al₂O₃ is formed on an emitting plane, ina semiconductor laser device of an embodiment 4.

[0066]FIG. 19C is a graph showing a refractive index distribution and anelectric field intensity distribution in the case where a firstprotective membrane comprising Nb₂O₅ is formed on an emitting plane, ina semiconductor laser device of an embodiment 4.

BEST MODE FOR CARRYING OUT THE INVENTION

[0067] The present invention will be explained below by using drawings,but the present semiconductor laser device is not limited to the devicestructure and the electrode structure shown in embodiments describedlater.

EMBODIMENT 1

[0068]FIG. 1 is a perspective view of an external shape of a laserdevice of an embodiment 1 of the present invention, FIG. 2 is across-sectional view along the II-II line in FIG. 1, and FIG. 3 is across-sectional view along the III-III line in FIG. 1.

[0069] The semiconductor laser device of the present embodiment 1 canafford excellent FFP by blocking the light released from parts otherthan a resonator plane with a shading layer 9. In a-specificconfiguration, a stripe-like convex part (ridge) 8 is provided in alaminate structure 100 in which a first electrically conductivesemiconductor layer 1, an active layer 3, a second conductive typesemiconductor layer 2 different from the first conductive type arelaminated (FIG. 2), and a stripe-like waveguide region is structured inthe vicinity of an active layer beneath this stripe-like ridge 8. And byboth ends vertical to a longitudinal direction of this ridge 8 as aresonator plane, a light resonator is formed in which a longitudinaldirection of a stripe is a resonating direction (light directingdirection). Of two resonator planes, one is a light emitting sideresonator plane (light emitting plane) having the function of mainlyemitting the light to the outside, and the other is a light reflectingside resonator plane (monitor plane) having the function of mainlyreflecting the light toward the inside of a waveguide region. Inaddition, on a side of a stripe-like convex part 8 and on the surface(upper plane) of a laminate structure directly connected to this side, afirst insulating membrane 10 is formed, a stripe-like ohmic electrode 5is provided which is ohmic-contacted with a second conductive typesemiconductor layer 2 on an upper plane of a convex part 8 of a secondelectrically conductive semiconductor layer on which this firstinsulating membrane 10 is not formed. In addition, on a first conductivetype semiconductor layer 1 exposed along a laminate structure 100, anohmic electrode 7 is formed in a stripe manner which is ohmic-contactedwith a first conductive type semiconductor layer 1. Both ohmicelectrodes are provided generally parallel. In the laser device of thepresent embodiment 1, further, a second insulating membrane 11 having anopening on each of these electrodes is formed so as to cover the wholedevice, and pad electrodes (n-side pad electrode 6, p-side pad electrode4) are formed, respectively, so as to contact with an ohmic electrodevia this second insulating membrane 11.

[0070] Herein, in the semiconductor laser device of the presentembodiment 1, as shown in FIG. 1 and FIG. 3, in the vicinity of a lightemitting side resonator plane, semiconductor layers on both sides of aridge are removed to below an active layer 3 and, thus, the device has,so to speak, a shape in which a corner part of a laminate structure 100is removed. Thereby, on a light emitting side, a resonator plane 101 ahaving a narrower width than that of a laminate structure 100 is formed,and the light is emitted from the resonator plane 101 a. In addition, onboth sides of a resonator plane 101 a on an emitting end side, a cornerpart of a laminate structure 100 is removed, whereby, a non-resonatorplane 101 b is formed which is situated on a different plane from thatof a resonator plane 101 a and is orthogonal with a resonatingdirection. Since a plane 101 b formed by removing a corner part of alaminate structure 100 reflects a part of the directed light but thereflected light is less than the light reflected by a resonator plane101 a and, thus, it does not substantially contribute to resonation ofthe light, the plane 101 b is called a non-resonator plane herein. Likethis, in the present embodiment 1, one of ends in a direction verticalto a light directing direction in a stripe-like waveguide region in alaminate structure is not a single plane but is formed so as to have aresonator plane 101 a which is a light emitting plane, and anon-resonator plane 101 b containing a cross-section of (stepwise)active layer which is situated rear a resonator plane. In addition,regarding a plane (side) parallel with a light directing direction in alaminate structure 100, on a light emitting side of the present laserdevice, a second side 102 a formed at a position nearer a central partof a waveguide region than a first side 102 which is a main side of alaminate structure is formed. And, in the laser device of an embodiment1, on the thus formed non-resonator plane 101 b and second side 102 a, ashading layer 9 is provided as shown in FIG. 3 and FIG. 4. FIG. 4 is aview, in which an insulating membrane and an electrode are omitted, forshowing clearly into what shape a shading layer is formed, in thesemiconductor of an embodiment 1 shown in FIGS. 1 to 3. In addition, anon-resonator plane 101 b and a second side 102 a are also called ashading layer forming plane. In FIGS. 1 and 4, symbols for theaforementioned respective planes are shown in parenthesis because thoseplanes do not appear on the surface.

[0071] In the laser device of an embodiment 1 structured as describedabove, the light generated in an active layer (light emitting region) isdirected mainly in a waveguide region and emitted through a resonator101 a to become a main beam (laser light). In the previous laser device,a part of the light is exuded from a waveguide region to become straylight which is transmitted in the device, and released from parts otherthan an emitting part of a resonator plane to the outside, which ismixed with a main beam released from a resonator plane to generate aripple, deteriorating FFP. However, in the laser device of the presentinvention, since a shading layer 9 is formed, this stray light can beblocked so as not to be released from parts other than a resonator plane101 a to the outside. It is suitable that a shading layer 9 provided asa layer for blocking stray light has the function of blocking the lightby reflecting and absorbing the light. When a shading layer 9 is formedby using a material which reflects the light, stray light can bereflected toward the inside of a device to improve the light outputefficacy. In addition, when a shading layer 9 is formed by using amaterial which absorbs stray light, stray light can be prevented frombeing released to the outside.

[0072] Generally, the light released from parts other than a resonatorplane to the outside is most frequently through an end in the vicinityof a resonator plane and, in a resonator end on a light emitting side,since the above light is released in the same direction as an emittingdirection for the laser light which is a main beam, those lights areeasily mixed. For this reason, as in the present embodiment 1, byprovision of a shading layer 9 which blocks the light in the vicinity ofa resonator plane, stray light can be effectively prevented from beingreleased to the outside. In the present embodiment 1, in particular, byforming a non-resonator plane 101 b on a plane different from aresonator plane 101 a and providing a shading layer 9 on this plane,stray light is effectively prevented from being released to the outsideand a ripple is prevented from generating in the laser light. Regardinga shading layer 9, a non-resonator plane may not be provided separatelyfrom a resonator plane as in the present embodiment 1, but a shadinglayer may be formed so as to limit an emitting part in a resonator planecomprising one plane as usual. However, in such the structure, since amain beam is blocked when a thickness of a light non-absorbable layerbecomes large, it is necessary to select a material through which thelight can not be transmitted even thin. However, as in the presentembodiment 1, by forming a resonator plane 101 a so as to be projectedfrom a non-resonator plane 101 b and providing a shading layer 103 onthe non-resonator plane 101 b, the shading layer may be formed thickwithout blocking a main beam. Further, since this leads to provision ofthe shading layer 103 in front of a light emitting plane (resonatorplane) 101 a, stray light can be more effectively blocked.

[0073] In addition, although stray light exuded from a waveguide regionis released not only from the aforementioned plane (end) in a directionvertical to a light directing direction but also from a plane (side)parallel with a directing direction, by providing a shading layer 9 alsoon a second side 102 a as shown in FIGS. 3 and 4, release of stray lightcan be prevented. When an insulating membrane, an electrode and the likeare provided on a side of a device, depending on materials for theinsulating layer and electrode, they themselves can be functioned as ashading layer. However, in the vicinity of a position where a wafer isdivided into devices, an insulating membrane and an electrode are notprovided for making division easy and a semiconductor layer is exposedin many cases. In such the case, as in the present invention, byprovision of a second side 102 a at a position near a waveguide regionto provide a shading layer 9, release of stray light to the outside canbe prevented and, thus, the laser light having better FFP without ripplecan be obtained.

[0074] As described above, the reason why stray light is generated isthat a width of a laminate structure is large relative to a width of awaveguide region directing the light. That is, the reason is that alayer through which the light can be transmitted like an active layer ispresent in a part other than a waveguide region (outside a waveguideregion). By excluding a part situated outside which does not constitutethis waveguide region, stray light can be excluded. By etching alaminate structure to a width equivalent to that of a waveguide region,a region through which stray light is directed can be excluded. However,since when a width of the whole laminate structure 100 (width of anactive layer) is made narrow, variation of that width becomes to greatlyinfluence on the properties of a device, it is necessary to control awidth with the better accuracy. However, as described later, in order tomake a waveguide region suitable for laser oscillation, a width of astripe is estimated to be around 5 μm at best, it is not easy to form awidth of all active layers by such the narrow width with the betteraccuracy control. In addition, even when formed with the betteraccuracy, a width is too small, the durability is lacked, difficulty isarisen upon formation of an electrode, being not practicable. In thepresent invention, taking these into consideration, a laminate having alarger width than that of a waveguide region is formed to provide astable stripe-like waveguide region (part held by a first side) and awaveguide region (part held by a second side), a width of which islimited to such an extent that no adverse effect is exerted on thedevice properties, in the laminate structure. And, a shading layer isprovided on a shading layer forming plane which is formed in order tostructure the waveguide region with a limited width.

[0075] In the present embodiment 1, a thickness of a shading layer 9 ispreferably 1500 Å to 3000 Å, more preferably 1500 Å to 5000 Å. When thethickness is smaller than 1500 Å, the light becomes difficult to betransmitted, being not preferable. On the other hand, when the thicknessis large, it is preferable that a shading layer 9 is provided so as tobury the removed part to the surface. By providing the shading layerthick, even when a width of an active layer becomes narrow, breakagedoes not easily occur.

[0076] In addition, as a material used in a shading layer 9, any of aconductor, a semiconductor and an insulator can be used. However, when aconductor is used, although the conductor may be provided so as tocontact directly with a laminate structure, in order to prevent shortcircuit and in order not to block the flow of current in a devicestructure, it is necessary to provide the conductor so as not to contactdirectly with an electrode by interposing an insulating membrane. Whenan insulating membrane is formed in advance, the same material as thatfor an electrode can be used and furthermore, the effect of shading thelight is enhanced. In addition, when a semiconductor is used, it ispreferable to use a semiconductor having a narrower band gap than thatof an active layer. When the band gap is wider than that of an activelayer, the light absorbing effect is obtained with difficulty, being notpreferable. When a semiconductor is used, after all necessary layers arelaminated, a shading layer may be formed by forming a shading layerforming plane by etching and performing lamination so as to bury theplane. Alternatively, after lamination is performed at least to a layerover an active layer, a reaction is stopped temporarily and parts otherthan an active layer constituting a waveguide region are removed toprovide a difference in level and, thereafter, a reaction may beinitiated again to perform lamination.

[0077] When an insulator is used, since it may contact with anelectrode, it is easily handled, but the light shading effect isrelatively inferior as compared with a conductor. Like this, in thepresent invention, since a shading layer can be formed by using variousmaterials, the most preferable material can be selected from thesematerials depending on a structure of a device, a step of manufacturinga device, a method for manufacturing a device and the like.

[0078] In addition, as a shading layer 9, a dielectric multi-layeredmembrane may be used. Thereby, the function of protecting an exposedend, in particular an active layer can be exerted in addition to theeffect of light shading.

[0079] As a specific material used in a shading layer 9, any materialselected from a simple substance of Ni, Cr, Ti, Cu, Fe, Zr, Hf, Nb, W,Rh, Ru, Mg, Al, Sc, Y, Mo, Ta, Co, Pd, Ag, Au, Pt and Ga, an alloy ofthem, a multi-layered membrane of them, and compounds such as oxides,nitrides and the like of them can be used as a conductor material. Thesemay be used alone or in combination of a plurality of them. A preferablematerial is material using Ni, Cr, Ti, Cu, Fe, Zr, Hf, Nb, W, Rh, Ru, Mgand Ga, and more preferable materials are materials using Ni, Cr, Ti,Ga, Rh and RhO. In addition, as a semiconductor material, Si, InGaN,GaAs and InP can be used. As an insulator material, TiO₂ and CrO₂ can beused. In order to form a material at a desired position, various methodssuch as vapor deposition, sputtering and the like can be used.

[0080] Among the aforementioned materials, in particular, Rh oxides suchas RhO preferable material. By using this RhO as a shading layer, thelight can be effectively shaded. Furthermore, because of a thermallystable layer, a shading layer can be obtained which is hardlydeteriorated in a step or upon use. In particular, by forming at aposition relatively far from a waveguide region, excellent FFP can beobtained without reducing the slope efficacy. In addition, this Rh oxidecan be particularly preferably used when a wavelength of a main beam isa wavelength of visible light from an ultraviolet to relatively shortwavelength. Specifically, by using the Rh oxide in a semiconductor laserdevice comprising a nitride semiconductor and having a wavelength of amain beam in a range of around 360 to 420 nm, the light shading effectbecomes larger and, thus, it is effective for blocking stray light andreducing a ripple.

[0081] In addition, in the present invention, by using a multi-layeredmembrane in a shading layer, a ripple can be effectively reduced. When ashading layer is in the form of a multi-layered membrane, amulti-layered membrane made of different materials may be used, or amulti-layered membrane made of the same materials may be used. Even inthe case of the same materials, since the property of a membrane can bealtered by changing a forming method or the like, a multi-layeredmembrane can be obtained in which optically or electrically differentlayers are laminated.

[0082] In addition, it is preferable that a shading layer 9 is formed soas to contact directly with a laminate structure as shown in anembodiment 1. Thereby, invasion of the light into the interior of partsother than a laminate structure, for example, an insulating membrane andthe like can be prevented, and release of stray light to the outside canbe effectively blocked. In particular, when a non-resonator plane 101 bis provided in the vicinity of a device separating plane, taking easyseparation and the like into consideration, a protective membrane andthe like are not provided on the surface near a separating plane (end)and the surface of a laminate structure is exposed in many cases and,therefore, it is preferable that a shading layer is formed directly onthe surface of an active layer of an exposed non-resonator plane of alaminate structure in the vicinity of this end.

[0083] However, in the present invention, when an insulating layer isformed on the surface of a laminate structure, a shading layer 9 may beformed on the insulating layer. This allows a material having the badadherability with a laminate structure to be used as a shading layer. Inaddition, by providing a shading layer on an insulating layer like this,there are the effect that contact with an electrode can be avoided andthe effect that diffusion of a material for a shading layer into alaminate structure can be suppressed even at heat treatment. Examples ofa material for an insulating layer include oxides such as SiO₂, ZrO₂ andthe like.

[0084] When such the insulating layer is used, it is preferable that This used as a shading layer and SiO₂ is used as an insulating layer. Byadopting such the structure, a shading layer having the excellent lightshading effect can be obtained and, further, absorption of the light canbe suppressed and, therefore, loss of the light which is directed in alaminate structure can be extremely suppressed to make the laser lighteffectively emit, and an excellent semiconductor laser device having asmall rise in Vf can be obtained. In addition, the aforementioned Rh andRh oxides such as SiO₂ and ZrO₂ may be provided in an insulating layer.

[0085] FIGS. 5 to 8 show an alteration example of an end structure on anemitting plane side in the present embodiment 1.

[0086] A non-resonating plane and a shading layer as an alterationexample are explained below by referring to FIGS. 4 to 8.

[0087] (Non-Resonator Plane)

[0088] In the present invention, a plane in a direction vertical to alight directing direction is an end, and a plane in a direction parallelwith a light directing direction is a side. In an embodiment 1, anon-resonator plane 101 b provided on a plane different from a resonatorplane is a plane vertical to a light directing direction and across-section of an active layer is exposed on the plane, provided thatit has no function as a resonator end. However, as described above, itis a plane through which the light exuded from a waveguide region can bereleased. In particular, in the vicinity of a resonator plane, the lightwhich is not the laser light is released in many cases. In the presentinvention, by providing a shading layer on a non-resonator planesituated on a plane different from a resonator plane, release of straylight to the outside is prevented.

[0089] As described above, a non-resonator plane 101 b is formed on aplane different from a resonator plane 101 a. A representative exampleis a plane provided by removing a corner part of a laminate structure asshown in FIGS. 4 to 6. However, the present invention is not limited tothis. For example, as shown in FIG. 8, two rectangular grooves 71putting a ridge between them are formed in an emitting side resonatorplane, a bottom surface orthogonal with a resonating direction of thegroove 71 may be used as a non-resonator plane 101 d. That is, in thepresent invention, like this, a non-resonator plane 101 d may be formedso as not to reach a side of a laminate structure. In addition, althoughnon-resonator planes are both formed at an end of a device in FIGS. 4 to6, as shown in FIG. 7, rectangular grooves 72 putting a ridge 8 betweenthem are formed on a side of an emitting side laminate structure, and aside orthogonal with a resonating direction of the groove 72 may be usedas a non-resonator plane 101 c. That is, in the present invention, anon-resonator plane may be provided in a middle of a stripe-likewaveguide of a laminate structure. Even in such the structure by aresonator plane and a non-resonating plane in a direction vertical to adirecting direction, and providing a shading layer 9 therein, straylight can be shaded. In addition, although it is preferable that anon-resonator plane 101 b is provided one by one on both sides putting aresonator plane between them, 2 or more is not problematic. When two ormore are provided, they may be isolated or close to each other. Inaddition, since it is suitable that a non-resonator plane faces adirection vertical to a light directing direction, it is not necessaryto be completely vertical but may be inclined.

[0090] (Second Side)

[0091] In the present invention, of planes (sides) in a directionparallel with a light directing direction, a second side is a plane on aside nearer a waveguide region, and a first side 102 is a plane situatedon an outer side than a second side. In the structure in FIGS. 7 and 8,a second side is expressed by attaching symbols of 102 c and 102 d. Bothof a first side and a second side contain a cross-section of an activelayer. In addition, a side of an n electrode forming plane and asubstrate side are a plane not containing an active layer, and a planeon which it is not necessary to provide a (not exposed) shading layer 9,but formation close to each other is not particularly problematic. Afirst side and a second side containing a cross-section of an activelayer can release the light exuded from a waveguide region like anon-resonator plane. In particular, in a part near a resonator plane,stray light is easily released. In the present invention, by forming ashading layer 9 on a second side in the vicinity of a resonator planeand situated near a waveguide region, release of stray light to theoutside is effectively prevented.

[0092] It is preferable that a second side is situated nearer awaveguide region than a first side and is provided in the vicinity of aresonating end, and it is particularly preferable that it is contactedwith a resonating end. Such the second side can be easily formed, forexample, by removing a corner part of a laminate structure as in FIG. 1,and a shading layer 9 can be easily formed. The reason is as follows:Although when a wafer is processed, a waveguide region is provided sothat it is successive between adjacent devices at a stage beforeseparation, when a shape as shown in FIG. 1 is adopted, since shadinglayers of two adjacent devices can be formed at the same time, it isadvantageous in respect of a step. However, a second side is notproblematic in order to prevent release of stray light even when notcontact with a resonating end. For example, as shown in FIG. 7, byforming a groove from a side at a part in a middle of a stripe of alaminate structure, a partial difference in level between a first sidemay be provided. In addition, in FIG. 8, although a first side and asecond side are formed so that they are overlapped (so that they areopposite at a part thereof, even in such the structure, sides are formedon different planes, respectively. By providing a shading layer on asecond side situated nearer a waveguide region, release of the straylight to the outside can be prevented. The number of this second sidemay be 1 or 2, or second sides may be isolated or close to each other.In addition, since a second side may not be completely parallel with alight directing direction, when it faces a plane parallel with adirecting direction, inclination is not problematic at all. In addition,as a plane in a direction parallel with a directing direction, otherthird and fourth sides may be provided at a position nearer a first sidefurthest from a waveguide region to form a side having a plurality ofdifferences in level, or a shading layer may be formed in that plane. Inaddition, when a stripe-like convex part (ridge) is formed, by forming asecond side so as to be situated on the same plane as a side wall (side)of the convex part 8 as shown in FIG. 3 (cross-sectional view in thevicinity of an emitting part in FIG. 1), there is a merit in respect ofa step such as sharing of a mask at etching and the like.

[0093] However, in the present invention, a second side may be situatedon a plane different from a side of a convex side. For example, as inFIG. 9, it may be formed outside a convex part 8. When a distancebetween second sides 102 e on both sides is larger than a width of astripe-like convex part (ridge) 8 as in this FIG. 9, the beam propertiesof the laser light in addition to the ripple reducing effect due to ashading layer can be changed depending on a distance between secondsides 102 e (a width of an active layer held by second sides). In otherwords, a width of an active layer held by second sides can beappropriately selected depending on the desired beam properties. Forexample, when a width of an active layer held by second sides 102 ebecomes small, the lateral light confining effect is enhanced, and anemission angle for the beam can be made large. A preferable range of awidth of an end of an active layer held by second sides is around 1.5 to10 μm, more preferably 4 to 8 μm, particularly preferably 5.5 to 7 μm.When a width of an active layer held by second sides (width of an activelayer of a resonator plane) exceeds 10 μm, a distance between a secondside and a waveguide region becomes large and, thus, the stray lightblocking effect is reduced. In addition, when the distance becomessmaller than 1.5 μm, the light confining effect becomes large and anemission angle becomes large and, thus, the light is concentrated toincrease load leading to easy occurrence of COD.

[0094] A shading layer in the present invention can prevent release ofstray light to the outside by effective shading by providing on both ofthe aforementioned non-resonator planes 101 b, 101 c and 101 d andsecond sides 102 a, 102 c and 102 d. In the present invention, it ispreferable that a shading layer is provided so that it is successivebetween a non-resonator plane and a second side as shown in FIG. 4.However, by providing on one of them as in FIGS. 5 and 6, the straylight release preventing effect can be obtained. In addition, aninclined plane may be used in which a non-resonator plane 101 b and asecond side 102 a become the same plane. Further, there is no problemeven when a shading layer 9 is provided on the surface, an end and aside of an exposed n-type layer, or on the surface, a side and an end ofa substrate 12. Since these are isolated from an emitting part even whenon the same plane as a resonator plane, the emitted light is hardlyshaded, being not problematic. Further, in addition, these may beprovided on a part of the surface (upper plane) of a p-type layerdirectly connected to a second side 102 a or a non-resonator plane 101b, provided that it is preferable that they are provided on the surfaceof a p-type layer other than a stripe-like convex part (ridge) 8. Likethis, since the light is leaked also through an upper plane of a p-typelayer in the vicinity of a light resonator plane 101 a, also by shadingthe light leaked from this, a ripple can be suppressed. Furthermore, anupper plane of a p-type layer is a plane in a different direction fromthat of a second side and that of a non-resonator end and, by forming itcontinuously also on a plane having such the positional relationship, itallows a shading layer to be hardly peeled. In particular, even a partwhich is difficult to be formed into a thin membrane layer such as acorner part and a edge part can obtain the firm adherability bysuccessive formation. Since a shading layer can be stably formed,deterioration of a layer itself can be prevented and, thus, the lifeproperties are also improved.

[0095] In addition, although it is preferable that a non-resonator planeand a second side are a flat and smooth plane, they may be rough orcurved. A shading layer formed on these planes is similar. However, evenwhen it is formed in conformity with the plane states of a non-resonatorplane and a second side, there is no problem. In addition, it may beformed in the different plane state depending on a position. Inaddition, for example, in a structure shown in FIG. 1, a boundary partbetween a second side and a non-resonator plane is structurally easy fora shading layer material to be deposited thereon. A corner part isformed thick, but it does not lead to deterioration in the effect of thelight non-transmittability, being not problematic.

[0096] In addition, since it is suitable that a shading layer 9 isprovided so as to cover a light transmitting layer in a second side anda non-resonator plane, it is suitably provided so as to cover at leastof a cross-section of an active layer, and it may not be formed on thewhole non-resonating end and second side. When a guiding layer or thelike is formed and, thus, a light-easily transmittable layer is presentin addition to an active layer, it is preferable that a shading layer isprovided so as to cover such the layer. In addition, in view of a step,a shading layer may be formed so as to cover up to an n-type layer and asubstrate.

[0097] In the semiconductor laser device of the present invention, ashading layer forming plane is formed on an end and a side. As a methodof forming these planes, a proper step and a method can be selecteddepending on a position for formation and a material for a shadinglayer. For example, it may be formed at the same time in an etching stepfor exposing an n-electrode forming plane, or it may be formed usingmasks having the same width or different width in an etching step forforming a stripe-like convex part. In addition, when it is formed beforeformation of a stripe-like convex part, a resonator plane with an activelayer having a narrower width can be obtained and, therefore, it becomespossible to form a shading layer at a position nearer a waveguide regionand, thus, by preventing mixing of stray light with a main beam andmaking a width of an active layer narrow, it becomes possible to form awaveguide structure excellent in the light confinement.

[0098] (Waveguide Region)

[0099] In the semiconductor laser device of the present invention, astripe-like waveguide region is formed mainly in the vicinity of anactive layer held by a first conductive type semiconductor layer and asecond conductive type semiconductor layer, and this stripe directionand a resonator direction are almost consistent. Herein, a waveguideregion is structured mainly in an active layer or in the vicinitythereof, and light guiding layers holding an active layer are formed toadopt a region up to guiding layers holding an active layer as a lightdirecting layer, which may be used as a waveguide region.

[0100] (Resonator Plane)

[0101] A pair of resonator planes formed on both ends of a waveguideregion are a flat plane which is formed by cleavage or etching. Whenformed by cleavage, it is necessary that a substrate and a laminatestructure layer have the cleaving property and, by utilizing thecleaving property, an excellent mirror plane can be easily obtained. Inaddition, when a resonator plane is formed by etching, etching times canbe reduced by formation at the same time with exposure of an n-electrodeforming plane. Alternatively, a resonator plane may be formed at thesame time in an etching step for forming a stripe-like convex part. Likethis, the number of steps can be reduced by formation at the same timewith each step. However, in order to obtain a more excellent resonatorplane, it is suitable that another step is set. In addition, areflecting membrane composed of a single membrane or a multi-layeredmembrane may be formed on a resonator plane thus formed by cleavage oretching, in order to effectively reflect the emitted light of an activelayer or adjust a refractive index. One of the resonator planes iscomposed of a plane having a relatively high reflective rate andfunctions mainly as a light reflection side resonator plane whichreflects the light toward inside a waveguide region, and the other iscomposed of a plane having a relatively low refractive index andfunctions mainly as a light emitting side resonator plane which emitsthe light to the outside.

[0102] (Stripe-like Convex Part)

[0103] In the semiconductor laser device of the present invention, astripe-like waveguide region can be easily formed by providing a convexpart on a laminate structure. Specifically, in a second electricallytype semiconductor layer in a laminate structure, a stripe-like convexpart is formed by removing both sides of a peak by etching or the likeso as to leave a central part in a peak manner, whereby, a stripe-likewaveguide region can be formed in the vicinity of an active layerbeneath the stripe-like convex part. A convex part is not limited to aforward mesa shape in which a width of a bottom side of the convex partis large and a stripe width becomes small as approaching an upper planeand, conversely, a convex part may be a reverse mesa shape in which astripe width becomes small as approaching a bottom of the convex part.Further, a convex part may be a convex part having a vertical side suchthat a width becomes constant irrespective of a position in a laminationdirection, or may be a shape in which these are combined. In addition,it is not necessary that a stripe-like waveguide has the same width overits full length. In addition, an embedded type laser device may beformed by re-growing a semiconductor layer on the surface of a convexpart after formation of such the convex part.

[0104] In the present invention, by partially changing a depth ofetching for forming the thus provided stripe-like convex part, adifference in level can be made in an active layer end and an activelayer side. For example, in FIG. 1, since both sides of a convex partare etched deeper than an active layer on a light emitting plane sideamong a stripe-like convex part, a difference in level is formed on anemitting plane side end and, as a result, a resonator plane and anon-resonator plane are formed. Further, on an emitting end side, asecond side successive to a side of a stripe-like convex part is formed,and the other side is a first side. By forming an end and a side so asto correspond to a stripe convex part like this, a plane on which ashading layer is provided can be formed effectively without via complexsteps.

[0105] A stripe-like convex part and a shading layer forming plane maybe formed in either order. As described above, a stripe-like convex partis formed in advance and, thereafter, a difference in level is set,whereby, formation corresponding to a stripe becomes easy. Since awaveguide region is formed corresponding to a stripe-like convex part,by forming a stripe in advance, a distance between a shading layerforming plane and a waveguide region can be controlled with the betteraccuracy.

[0106] In addition, a part of an active layer may be removed in advanceand, thereafter, a stripe-like convex part may be provided correspondingto the removed position. When a stripe-like convex part is formed inadvance, it is difficult to form an active layer held by second sidesnarrower than a width of a convex part because it is technicallydifficult to form a mask having a further narrower width on astripe-like convex part after formation of the convex part. However, ona relatively large flat plane before formation of a stripe-like convexpart, it is relatively easy to form a mask thinner than a mask to beformed for forming a ridge. Therefore, a thin mask is formed on a parton which a narrow active layer held by second sides is to be formed (amasked part is a part on which a narrow active layer held by secondsides is to be formed), and parts on both sides thereof are etched tobelow an active layer to form first a shading layer forming plane. Uponthis, on the whole part other than both sides of the thin mask, a maskis formed. And, thereafter, a material which is to be a shading layer isembedded into a part removed by etching to the same level as the surfaceof a semiconductor layer. Then, a mask for forming a ridge is formed andboth sides of the mask are etched to form a ridge. By doing so, as shownin FIG. 10, an active layer having a smaller width than that of a convexpart 8 in the vicinity of an emitting plane can be formed. Thereby, thetransverse light can be confined more strongly. In addition, in thatcase, by growing a suitable semiconductor layer outside a second side soas to embed at least a side of a thinly formed stripe-like active layer,breakage of the vicinity of an emitting end can be prevented uponformation of a resonator plane by cleavage.

[0107] In the present invention, as described above, by providing a parthaving a small width of an active layer on an emitting end side of alaminate structure to form a shading layer forming plane, a structurecan be obtained which effectively prevents release of stray light to theoutside and, at the same time, by changing a width of an active layerlike this, the directing properties of a waveguide can be changed. Inparticular, when a second side is formed so that a width of an activelayer becomes small to the vicinity of a waveguide region, it completelyresults in a difference in refractive index (not an effective differencein refractive index but actual difference in refractive index) and,therefore, the controllability of the transverse mode becomesparticularly better. To the contrary, since a part having a first sideis a waveguide region in which a difference in refractive index iseffectively set by formation of a stripe-like convex part, a region inwhich a difference in refractive index is completely set and a region inwhich a difference in refractive index is effectively set are formed inone continuous waveguide region in the present embodiment. When this isutilized, a divergence angle of the emitted light can be adjusted in thelaser device of the present embodiment.

[0108] (Laminate Structure)

[0109] In the semiconductor laser device of the present invention, as asemiconductor used as a first conductive type semiconductor layer, anactive layer or a second conductive type semiconductor layer of alaminate structure, nitride semiconductors such as GaN, AlN and InN, andIII-V Group nitride semiconductors (In_(x)Al_(y)Ga_(1−x−y)N, 0≦x, 0≦y,x+y≦1) which are a mixed crystal of the above nitride semiconductors canbe used. A preferable example using nitride semiconductors will bespecifically explained below regarding the semiconductor laser device ofthe present invention. Herein, a laser device using a nitridesemiconductor is a semiconductor laser device using a nitridesemiconductor in any layer of a laminate structure in which a firstconductive type semiconductor layer, an active layer, and a secondconductive type semiconductor layer are laminated in this order,preferably a semiconductor laser device using a nitride semiconductor inall layers. Specifically, a cladding layer having a nitridesemiconductor is provided in a first conductive type semiconductor layerand a second conductive type semiconductor layer, respectively, and awaveguide is formed in an active layer and in the vicinity thereof. As amore preferable structure of a semiconductor laser device structured byusing a nitride semiconductor (nitride semiconductor laser device), ann-type nitride semiconductor layer is used in a first conductive typesemiconductor layer, a p-type nitride semiconductor layer is used in asecond electrically type semiconductor layer, and a layer containing anitride semiconductor layer containing In is used in an active layer.

[0110] (Nitride Semiconductor)

[0111] As a nitride semiconductor used in the laser device of thepresent invention, there are GaN, AlN, and InN, and III-V Group nitridesemiconductors (In_(b)Al_(d)Ga_(1−b−d)N, 0≦b, 0≦d, b+d≦1) which are amixed crystal of GaN and the like. In addition, B can be used as a IIIGroup element, or a mixed crystal in which a part of N of a V Groupelement is replaced with As or P may be used. In addition, eachconductive type impurity can be added to such the nitride semiconductorto obtain the desired conductive type. As an n-type impurity used in anitride semiconductor, specifically, IV Group and VI Group elements suchas Si, Ge, Sn, S, O, Ti, Zr and the like can be used, preferably Si, Geand Sn are used, more preferably Si is used. In addition, as a p-typeimpurity, specifically, there are Be, Zn, Mn, Cr, Mg and Ca, preferablyMg is used. A laser device using a nitride semiconductor will bespecifically explained below regarding the laser device of the presentinvention. Herein, a laser device using a nitride semiconductor meansthat a nitride semiconductor is used in any layer of a laminatestructure in which a first conductive type layer, an active layer, and asecond conductive type layer are laminated, preferably in all layers.For example, a cladding layer comprising a nitride semiconductor isprovided in a first conductive type layer and a second conductive typelayer, respectively, and an active layer is provided between those twocladding layers to form a waveguide. More specifically, a firstconductive type layer contains an n-type nitride semiconductor layer, asecond conductive type layer contains a p-type nitride semiconductorlayer, and an active layer contains a nitride semiconductor containingIn.

[0112] In addition, in the nitride semiconductor laser device of thepresent invention, when an n-type cladding layer and a p-type claddinglayer are provided to structure a waveguide region, a guiding layer andan electron confining layer may be provided between each cladding layerand an active layer.

[0113] A preferable structure of each layer in the nitride semiconductorlaser element of the present invention will be explained below.

[0114] (N-Type Cladding Layer)

[0115] In the laser device using a nitride semiconductor of the presentinvention, as a nitride semiconductor used in an n-type cladding layer,it is enough that a sufficient difference in refractive index forconfining the light is set as in a p-type cladding layer, and a nitridesemiconductor layer containing Al is preferably used. In addition, thislayer may be a single membrane or a multi-layered membrane.Specifically, as shown in examples, a superlattice structure in whichAlGaN and GaN are laminated alternately may be used. In addition, thisn-type cladding layer acts as a carrier confining layer and a lightconfining layer and, in the case of a multi-layered structure, asdescribed above, a nitride semiconductor containing Al, preferably AlGaNmay be grown. Further, this layer may be doped with an n-type impurity,or may be undoped. Alternatively, in a multi-layered membrane layer asshown in examples, at least one layer constituting the layer may bedoped. In a laser device having an oscillating wavelength of longwavelength 430 to 550 nm, this cladding layer is preferably GaN dopedwith an n-type impurity. In addition, a membrane thickness is notparticularly limited as in a p-type cladding layer, but by forming alayer at not less than 100 Å and not more than 2 μm, preferably byforming a layer in a range of not less than 500 Å and not more than 1μm, the sufficient function as a light confining layer is exerted.

[0116] (Active Layer)

[0117] In the present invention, when the semiconductor laser device ofthe present invention is structured by using a nitride semiconductor,inclusion of a nitride semiconductor layer containing In in an activelayer can generate the laser light in a wavelength region of anultraviolet region and a visible region from blue to red. In addition, anitride semiconductor layer containing In causes extremely importantdevice deterioration in driving a laser device in some cases when anactive layer is exposed to the air. However, in the present invention,since a waveguide region isolated from an emitting part is a waveguideregion structured by a ridge provided at a depth not reaching an activelayer, it is possible to suppress such the device deterioration tominimum. The reason is as follows: Since In has a low melting point, anitride semiconductor containing In is a material which is easilydegraded and vaporized, and easily undergoes breakage at etching or thelike. In addition, in processing after exposure of an active layer, itbecomes difficult to retain its crystallinity and, as a result, it leadsto shortening of the device life.

[0118] Herein, an active layer may be a quantum well structure and, inthat case, may be a single quantum well or a multiple quantum well.Preferably, by adopting a quantum well structure, a laser device and anedge emitting device excellent in the emitting efficacy and having thehigh output can be obtained. It is preferable that, as an active layerof a nitride semiconductor, as described above, a nitride semiconductorcontaining In is used. Specifically, it is preferable to use a nitridesemiconductor represented by Al_(x)In_(y)Ga_(1−x−y)N(0≦x≦1, 0≦y≦1,x+y≦1). It means that, in this case, in an active layer having a quantumwell structure, it is preferable to use nitride semiconductors shownherein as a well layer. In addition, a wavelength region from nearultraviolet to green of the visible light (380 nm to 550 nm), it ispreferable to use In_(y)Ga_(1−x−y)N(0<y<1). In addition, also in awavelength region longer than that (red), similarly,In_(y)Ga_(1−y)N(0<y<1) can be used. Upon this, mainly by changing an Incrystal mixing ratio y, the desired wavelength can be obtained. In ashort wavelength region of not more than 380 nm, since a wavelengthcorresponding to a band gap of GaN is 365 nm and since the band gapenergy which is almost the same as the band gap energy for GaN orslightly larger is necessary, for example,Al_(x)In_(y)Ga_(1−x−y)N(0≦x≦1, 0<y≦1, x+y≦1) is used.

[0119] When an active layer has a quantum well structure, by adopting arange of not less than 10 Å and not more than 300 Å, preferably a rangeof not less than 20 Å and not more than 200 Å as a specific membranethickness of a well layer, Vf (threshold current density) can bereduced. In addition, from a viewpoint of the crystal growth, when thethickness is 20 Å or more, a layer not having a great scatter in amembrane thickness and having the relatively uniform membraneousproperties can be obtained. By adopting 200 Å or less, the crystalgrowth suppressing occurrence of crystal defect low becomes possible.The number of well layers in an active layer is not particularly limitedbut is 1 or more. Upon this, when the number of well layers is 4 ormore, if a thickness of each layer constituting an active layer becomeslarge, a thickness of the whole active layer becomes large, leading toincrease in Vf. Therefore, it is preferable to suppress a thickness ofan active layer low by adopting a range of 100 Å or less as a thicknessof a well layer. In high output LD, by adopting not less than 1 and notmore than 3 as the number of well layers, there is a tendency that adevice having the high emitting efficacy is obtained, being preferable.

[0120] In addition, a well layer may be doped with a p- or n-typeimpurity (acceptor or donor), or undoped or non-doped. However, when anitride semiconductor containing In is used as a well layer, since thereis a tendency that the crystallinity is deteriorated when the n-typeimpurity concentration becomes large, it is preferable that the n-typeimpurity concentration is suppressed low to obtain a well layer havingthe better crystallinity. Specifically, it is preferable to grow a welllayer undoped in order to maximize the crystallinity better.Specifically, it is preferable that the n-type impurity concentration is5×10¹⁶/cm³ or less. The state where the n-type impurity concentration is5×10¹⁶/cm³ or less is the state where the impurity concentration isextremely low, and this state can be said to be a well layer containingsubstantially no n-type impurity. In addition, where a well layer isdoped with the n-type impurity, when doped with the n-type impurityconcentration of a range of not less than 1×10¹⁸ and not more than5×10¹⁶/cm³, deterioration of the crystallinity can be suppressed low andthe carrier concentration can be increased.

[0121] The composition of a barrier layer is not particularly limitedbut the same nitride semiconductor as that for a well layer can be used.Specifically, a nitride semiconductor containing In such as InGaN havinga lower In crystal mixing ratio than that of a well layer, and a nitridesemiconductor containing Al such as GaN, AlGaN and the like can be used.Upon this, it is necessary that a barrier layer has greater band gapenergy than that of a well layer. As the specific composition,In_(β)Ga_(1−β)N (0≦β<1, α>β), GaN, Al_(γ)Ga_(1−γ)N (0<{cube root}<1) canbe used, preferably In_(β)Ga_(1−β)N (0≦β<, α>β) and GaN can be used toform a barrier layer with the better crystallinity. The reason is asfollows: When a well layer comprising a nitride semiconductor containingIn is grown directly on a nitride semiconductor containing Al such asAlGaN, there is a tendency that the crystallinity is reduced and thefunction of a well layer is deteriorated. When Al_(γ)Ga_(1−γ)N (0<γ<1)is used as a barrier layer, this can be avoided by providing a barrierlayer containing Al on a well layer and providing a multi-layeredmembrane barrier layer using a barrier layer of In_(β)Ga_(1−β)N (0≦β<1,α>β) and GaN under a well layer. Like this, in a multiple quantum wellstructure, a barrier layer held by well layers is not particularlylimited to one layer (well layer/barrier layer/well layer) but aplurality of barrier layers having the different composition, impurityamount and the like may be provided such as a barrier layer of 2 or morelayers, “well layer/barrier layer (1)/barrier layer (2)/ . . . /welllayer”. Herein, α is an In constituent ratio for a well layer, and it ispreferable that an In constituent ratio β for a barrier layer is smallerthan that for a well layer by adopting α>β.

[0122] A barrier layer may be doped with the n-type impurity, or may beundoped. Preferably, a barrier layer is doped with the n-type impurity.Upon this, it is preferable that the n-type impurity concentration in abarrier layer is at least 5×10¹⁶/cm³ or more, and the upper limit is1×10²⁰/cm³. Specifically, for example, in the case of LD for which thehigh output is not required, it is preferable that the n-type impurityis contained at a range of not less than 5×10¹⁶/cm³ and not more than2×10¹⁸/cm³. In addition, in the case of LD having the higher output, itis preferable to dope at a range of not less than 5×10¹⁷/cm³ and notmore than 1×10²⁰/cm³, preferably at a range of not less than 1×10¹⁸/cm³and not more than 5×10¹⁹/cm³. When doped at the high concentration likethis, it is preferable that a well layer contains substantially non-type impurity, or a well layer is grown undoped. By doping at theaforementioned preferable range, as described above, carriers can beinjected at the high concentration with the better crystallinity.

[0123] When doped with the n-type impurity, all barrier layers in anactive layer may be doped, or a part of barrier layers may be doped withthe n-type impurity. When a part of barrier layers are doped with then-type impurity, it is preferable to dope a barrier layer arranged on ann-type layer side in an active layer. Specifically, by doping an n-thbarrier layer Bn (N=1,2,3 . . . ) counting from an n-type layer side,electrons are effectively injected in an active layer and, thus, adevice excellent in the emitting efficacy and the inner quantum efficacycan be obtained. This is not limited to a barrier layer but is also truein the case of a well layer. When both are doped, by doping an n-thbarrier layer Bn (N=1, 2, 3 . . . ) and a m-th well layer Wm (m=1,2,3 .. . ) counting from an n-type layer, that is, by doping starting with aside near an n-type layer, there is a tendency that the aforementionedeffects can be obtained.

[0124] A-thickness of a barrier layer is not particularly limited, but500 Å or less, more particularly a range of not less than 10 Å and notmore than 300 Å as in a well layer can be applied.

[0125] In a laser device using a nitride semiconductor of the presentinvention, a laminate structure is preferable in which a firstconductive type layer has an n-type nitride semiconductor and a p-typenitride semiconductor is used in a second conductive type layer.Specifically, an n-type cladding layer and a p-type cladding layer areprovided in each conductive type layer to structure a waveguide. Uponthis, a guiding layer and an electrode confining layer described latermay be provided between each cladding layer and an active layer.

[0126] (P-Type Cap Layer)

[0127] As a p-type cap layer provided between a p-type cladding layerand an active layer, AlGaN and the like can be preferably used, leadingto a layer having the effect of confining carriers in an active layerand, since a threshold current can be reduced, easy oscillation becomespossible. AlGaN may be doped with the p-type impurity, or may benon-doped. A thickness is preferably 500 Å or less.

[0128] (Guiding Layer)

[0129] In the present invention, by providing p-type and n-type guidinglayers holding an active layer on inner side than a cladding layer(active layer side) to form a light waveguide, an excellent waveguidecan be formed. Upon this, a thickness of a waveguide (active layer andboth guiding layers holding it) is preferably 6000 Å or less. When athickness is 6000 Å or less, rapid increase in an oscillation thresholdcurrent can be suppressed. More preferably, by adopting 4500 Å or less,continuous oscillation becomes possible at a base mode and a long lifewith low-suppressed oscillation threshold current. In addition, bothguiding layers are formed at the almost same thickness, preferably notless than 100 Å and not more than 1 μm, more preferably not less than500 Å and not more than 2000 Å. As a nitride semiconductor used in aguiding layer, refractive index suitable for forming a waveguide isselected by comparing with a cladding layer to be provided on itsexternal side, and a single membrane or a multi-layered membrane may beused. Specifically, undoped GaN is preferable at an oscillationwavelength of 370 nm to 470 nm, and a multi-layered membrane structureof InGaN/GaN is preferably used at a relatively long wavelength region(450 nm or more).

[0130] (P-Type Cladding Layer)

[0131] In a laser element using a nitride semiconductor of the presentinvention, it is preferable that a p-type cladding layer containing ap-type nitride semiconductor (first p-type nitride semiconductor) isprovided as a second conductive type layer or a first conductive typelayer. Upon this, an n-type cladding layer containing an n-type nitridesemiconductor is provided on an conductive type layer different from anconductive type layer on which a p-type cladding layer is provided, toform a waveguide in a laminate structure. In addition, as a nitridesemiconductor used in this p-type cladding layer, it is enough that asufficient difference in refractive index for confining the light isset, and a nitride semiconductor layer containing Al is preferably used.In addition, this layer may be a single or multi-layered membrane.Specifically, as shown in examples, the layer may be a superlatticestructure in which AlGaN and GaN are laminated alternately. Thesuperlattice structure makes the crystallinity better, being preferable.Further, this layer may be doped with the p-type impurity, or may beundoped. Alternatively, as shown in examples, in a multi-layeredmembrane layer, at least one layer constituting it may be doped. In alaser device having an oscillation wavelength of long wavelength 430 to550 nm, this cladding layer is preferably GaN doped with the p-typeimpurity. A thickness is not particularly limited, but a p-type claddinglayer functions as a sufficient light confining layer by formation in arange of not less than 100 Å and not more than 2 μm, preferably byformation in a range of not less than 500 Å and not more than 1 μm.

[0132] In the present invention, an electron confining layer and a lightguiding layer described later may be provided between an active layerand a p-type cladding layer. Upon this, when a light guiding layer isprovided, a structure is preferable in which a light guiding layer isprovided also between an n-type cladding layer and an active layer tohold an active layer by light guiding layers. In this case, an SCHstructure is obtained, and a difference in refractive index is set byrendering an Al constituent ratio for a cladding layer greater than anAl constituent ratio for a guiding layer, and the light is confined by acladding layer. When a cladding layer and a guiding layer are formed ofa multi-layered membrane, respectively, a magnitude of an Al constituentratio is determined by an Al average composition.

[0133] (P-Type Electron Confining Layer)

[0134] In addition, a p-type electron confining layer provided betweenan active layer and a p-type cladding layer, preferably between anactive layer and a p-type light guiding layer is a layer which functionsto confine carriers in an active layer, and contributes to eachoscillation by reducing a threshold current. Specifically, AlGaN isused. In particular, by adopting a structure in which a p-type claddinglayer and a p-type electron confining layer are provided in a secondconductive type layer, the more effective electron confining effect canbe obtained. When AlGaN is used in this p-type electron confining layer,preferably by doping with the p-type impurity, the aforementionedfunction can be assuredly exerted, but even a non-doped layer has theaforementioned carrier confining function. A lower limit of a thicknessis at least 10 Å, preferably 20 Å. In addition, the aforementionedeffects can be sufficiently expected by formation at a thickness of 500Å or less and adopting x of 0 or more, preferably 0.2 or more in thecomposition of Al_(x)Ga_(1−x)N. In addition, an n-side carrier confininglayer which confines holes in an active layer also on an n-type layerside. Confinement of holes is possible unless offset (difference of aband gap between an active layer) is set to an extent for electronconfinement. Specifically, the same composition as that for a p-sideelectron confining layer can be applied. In addition, in order to renderthe crystallinity better, the layer may be formed of a nitridesemiconductor containing no Al. Specifically, almost the samecomposition as that for a barrier layer in an active layer can be used.In this case, it is preferable that an n-side barrier layer for carrierconfinement is arranged on the most n-type layer side in an activelayer, or it may be arranged in an n-type layer in contact with anactive layer. Like this, by providing p-side and n-side carrierconfining layers, preferably in contact with an active layer, thoselayers can inject carriers effectively into an active layer-or a welllayer. As another form, in an active layer, a layer in contact with ap-side or n-side layer can be used as a carrier confining layer.

[0135] (Electrode)

[0136] In the semiconductor laser device of the present invention, ap-side electrode formed on a stripe-like convex part and an n-sideelectrode provided on an n-side layer (n-type contact layer) are notparticularly limited, but a material which can obtain better ohmiccontact with a nitride semiconductor can be preferably used. Byformation corresponding to a stripe-like convex part which is to be awaveguide region, injection of carriers can be effectively performed.Alternatively, a nitride semiconductor may be provided in contacttherewith via an insulating membrane described later. Alternatively, anohmic electrode provided in contact with a semiconductor, and a padelectrode comprising a material suitable for bonding may be provided. Inthe present embodiment, a structure is obtained in which after a firstinsulating membrane is formed, an opening is provided to form an ohmicelectrode, a first insulating membrane having an opening is furtherformed thereon, and a pad electrode is formed thereon. As a specificmaterial, there are Ni, Co, Fe, Ti, Cu, Rh, Au, Ru, W, Zr, Mo, Ta, Ptand Ag and oxides and nitrides of them in the case of a p-sideelectrode. Thus, a single layer, an alloy or a multi-layered membrane ofthe foregoing may be used. In the case of an n-side electrode, there areNi, Co, Fe, Ti, Cu, Rh, Au, Ru, W, Zr, Mo, Ta, Pt, Ag and the like, anda single layer, an alloy or a multi-layered membrane of them can beused.

[0137] (Insulating Membrane)

[0138] In the semiconductor laser device of the present invention, it ispreferable that a protective membrane is formed on a side of astripe-like convex part and on an exposed surface (plane) continuing tothe side. When formed only on a part for protecting a convex part, theinsulating property does not matter, but by using an insulatingprotective membrane, a membrane can be obtained which has the functionas an insulating membrane for preventing short circuit betweenelectrodes and the function as a protective membrane for protecting anexposed layer. Specifically, a single membrane or a multi-layeredmembrane of SiO₂, TiO₂ and ZrO₂ can be preferably used. Alternatively,as described above, an insulating membrane may be formed into amulti-layered membrane via an electrode.

[0139] Herein, in a laser device using a nitride semiconductor, bysetting a position on which a stripe-like ridge is to be provided in anitride semiconductor layer containing Al and providing an insulatingmembrane on the surface of an exposed nitride semiconductor and on aconvex part side, better insulation is obtained and, thus, even when anelectrode is provided on an insulating membrane, a laser device withoutleak current can be obtained. The reason is as follows: Since there ishardly a material which can ohmic-contact better among a nitridesemiconductor containing Al, even when an insulating membrane and anelectrode are provided on the surface of this semiconductor, suitableinsulation is attained such that leak current is hardly generated.Conversely, when an electrode is provided on the surface of a nitridesemiconductor containing no Al, ohmic contact is easily formed between amaterial for the electrode and a nitride semiconductor and, when anelectrode is formed on the surface of a nitride semiconductor containingno Al via an insulating membrane, it becomes a cause for leakage whenfine holes are present on an insulating membrane due to the membraneousproperties of an insulating membrane and an electrode. For this reason,in order to solve them, such a consideration is necessary that aninsulating membrane is formed at a thickness at which insulation issufficiently maintained, or a shape and a position of an electrode isnot imposed on the surface of an exposed semiconductor and, thus, agreat limitation arises in designing a laser element structure. inaddition, a position on which a ridge (convex part) is to be provided isimportant. The surface (plane) of nitride semiconductors on both sidesof a ridge which is exposed at formation of a ridge (convex part)occupies an extremely great area as compared with a ridge (convex part)side and, by maintaining the better insulating property on this surface,a laser device having high design degree of freedom to which variouselectrode shapes can be applied and for which an electrode formationposition can be selected comparatively freely can be obtained, beingextremely advantageous in formation of a ridge (convex part). Herein, asa nitride semiconductor containing Al, specifically, AlGaN, or theaforementioned a superlattice multi-layered membrane structure ofAlGaN/GaN is suitably used.

EMBODIMENT 2

[0140] In the semiconductor laser device of an embodiment 2 of thepresent invention, like an embodiment 1, by providing a shading membranein the vicinity of a resonator plane, release of the light exuded from awaveguide region (stray light) to the outside is prevented, and has thesame structure as that of an embodiment 1 except that, in order to forma shading membrane to be peeled with difficulty, a light-transmittablemembrane 9 a comprising the same elements as those constituting ashading membrane is provided between a shading membrane and a laminatestructure (FIG. 13A-FIG. 13C).

[0141] In the laser device of this embodiment 2, a membrane having thedesired shading property is formed on the surface of a laminatestructure with the better adherability, by utilizing the fact that evencompounds constituted by the same element have the different physicalproperties and chemical properties when a constituent ratio isdifferent. It means that, for example, when an oxidized membrane of theparticular metal is used as a shading membrane, an oxide having anoxygen rate different from that of a shading membrane is used as alight-transmittable membrane between a shading membrane and a laminatestructure. More specifically, it means that an oxide containing muchoxygen which is highly light-transmittable is used as alight-transmittable membrane, and an oxide containing much metal whichhighly shades the light is used as a shading membrane. Like this, whenthe content of a metal is changed from small to large, the lighttransmittance of some materials is greatly changed. In this embodiment2, the materials having such the nature can be used. In addition, suchthe membrane can be easily obtained by changing the conditions atmembrane formation. The conditions at growth to be changed are theconditions changeable in an apparatus used for forming a membrane, suchas a flow rate and a constituent ratio of a gas to be used, and a gassupplying direction, as well as the vacuum degree, the atmosphere, atemperature and the like in an apparatus.

[0142] If materials having the different transmittance are simplyprovided, the effect of shading the light can be obtained also byforming a metal layer on an insulating light-transmittable membrane suchas SiO₂. However, there are cases where a process for production isdifferent using a different material as a raw material or a problem ofthe adherability arises. In response thereto, if the optical propertiescan be changed by using the same raw material and only by changing themembrane forming conditions in the same apparatus, since a membrane canbe prepared continuously, mixing of a foreign matter can be prevented.In the present embodiment 2, between this light-transmittable membraneand a shading membrane, an intermediate membrane having the lighttransmittance which is between the transmittances of both membranes maybe formed. Like this, by changing the transmittance gradually, the lightcan be almost completely blocked by a shading membrane. Like this, whenlaminated in combination of membranes having the constituent elements, aprotective membrane (shading membrane) having the extremely excellentadherability can be obtained as compared with the case where membranescomprising different elements are laminated.

[0143] In addition, a light-transmittable membrane and a shadingmembrane can be formed by a composition graded layer by changing theconditions gradually and successively instead of a method for forming amulti-layered membrane by step-wisely changing the membrane formingconditions. Even in such the case, since it is enough that thecomposition is finally changed to that which can block the light, in thepresent invention, such the composition graded membrane may be amembrane in which an underside of the membrane (side in contact with alaminate structure) is light-transmittable and, as a position at ahigher level, the light transmittability is lowered, that is, the lightshading property is enhanced.

[0144] As a method for forming a light-transmittable membrane and ashading membrane on the surface of a laminate structure, there are gasphase growing methods such as physical vapor deposition method (PVDmethod) and chemical vapor deposition method (CVD method). By changingthe conditions when these methods are used, membranes having thedifferent constituent ratio can be easily obtained. In the presentinvention, it is preferable that the PVD method is used, and asputtering method and a vacuum vapor deposition method may be used. Whensuch the methods are used, since a light-transmittable membrane and ashading membrane comprising the same elements as in the presentinvention are formed using the same raw material, a membrane can beformed successively. For this reason, mixing of impurities and the likecan be prevented to form a membrane having the high purity, and a timenecessary for exchanging a raw material is not necessary. By formationby changing the conditions, a shading membrane having both of thetightness and optical property can be formed. As a preferable materialused in a shading membrane and a light-transmittable membrane, materialswhich can change the light transmittance by changing a constituent ratioare preferable. Examples of the preferable material include oxides,nitrides and fluorides of metals. Specific materials are Rh, Si, Ti, Al,Cr, Nb, Mg, V, Fe, Co, Ni, Cu, Zn, Ga, Y, Zr, Mo, Ru, Pd, Ag, Sn, In,Hf, Ta, W, Ir, Pt and Au. These may be used alone or in combination of aplurality of them.

[0145] In addition, a membrane having the different crystallinitycorresponding to a constituent ratio may be used. Since when thecrystallinity is different, the optical property is also changed byutilizing this, a membrane having the shading property can be formedwith the better adherability. For example, a membrane having the highcrystallinity is used as a light-transmittable membrane, and a membranehaving the low crystallinity can be used thereon as a shading membrane.This utilizes the fact that a membrane having the high crystallinity isformed compact and easily produces a membrane having the hightransmittance and having the uniform crystallinity and, in addition,since a membrane having the low crystallinity is a crystal lattice whichis irregular to the light, its light transmittability is easilydecreased. In the case of membrane formation by a sputtering method orthe like, when one tries to form an irregular crystal having the shadingproperty by rendering the conditions (for example, air pressure) mild,there is an atendency that a peelable membrane is obtained. However,instead of forming such the membrane directly on a semiconductor layer,by forming on a compact light-transmittable membrane comprising the sameelements having the better crystallinity, the formed membrane can beused as a shading membrane.

[0146] In addition, in the present invention, among the aforementionedmaterials, in particular, Rh oxides (a representative of which is RhO)are a preferable material as a material forming a shading membrane and alight-transmittable membrane. By using this Rh oxide as a shadingmembrane and as a light-transmittable membrane, a membrane which caneffectively shade the light can be formed with the better adherability.Furthermore, since the Rh oxide is thermally stable, a stable shadingmembrane can be obtained in which deterioration hardly occurs in a stepor upon use. In particular, by formation at a position in the vicinityof a resonator plane and slightly isolated from a resonator plane,excellent FFP can be obtained without reducing the slope efficacy. Inaddition, this Rh oxide can be particularly preferably used in a laserdevice in which a wavelength of a main beam is in a region from anultraviolet to a comparatively-short wavelength visible region.Specifically, by using in a semiconductor laser device comprising anitride semiconductor and having a wavelength of a main beam in a rangeof around 360 to 420 nm, since the light shading effect can be enhanced,it is advantageous to block stray light and reduce a ripple.

[0147] A total thickness of a shading membrane is preferably 500 Å to10000 Å, more preferably 1000 Å to 5000 Å. When a thickness is smallerthan 1000 Å, the light is easily transmitted and the shading effect isreduced, being not preferable.

[0148] In addition, a total thickness of a light-transmittable membraneis preferably 100 Å to 1000 Å, more preferably 200 Å to 600 Å. When athickness is smaller than 200 Å, a light-transmittable membrane itselfbecomes peelable, being not preferable. In addition, when a thickness istoo large, the productivity is reduced, being not preferable.

[0149] In addition, a thickness as a protective membrane in combinationof a shading membrane and a light-transmittable membrane is preferably atotal thickness of 500 Å to 20000 Å including the case where anintermediate layer is provided therebetween.

[0150] In addition, as a position on which a shading membrane is to beprovided, the vicinity of a resonator plane is preferable. The positionmay be on the same plane as a resonator end or on the different planefrom a resonator end. Preferably, a shading membrane is formed on thedifferent plane. Specifically, as in an embodiment 1, ends on both sidesof a resonator plane are removed below an active layer in the vicinityof a light emitting side resonator plane, and a corner part of alaminate structure is removed. By the foregoing, the laser device of anembodiment 2 has the same actions and effects as those of the laserdevice of an embodiment 1.

EMBODIMENT 3

[0151] The semiconductor laser device of an embodiment 3 of the presentinvention has at least two protective membranes (first protectivemembrane 109, and a second protective membrane 110 having the lowertransmittance than that of the protective membrane 109) having thedifferent light transmittance on an end in a direction vertical to alight resonating direction, and controls release of the light from anend by provision of two protective membranes having the different lighttransmittance on an end. Specific forms are shown in FIGS. 14A to 14C.In a view of the figure in an embodiment 3, the same parts as those ofan embodiment 1 are shown by attaching the same symbols. FIG. 14C is anXIVC-XIVC cross-sectional view of FIG. 14A. In the present embodiment 3,as shown in FIG. 14C, a stripe-like convex part (ridge) 8 is provided ina laminate structure in which a first conductive type semiconductorlayer (n-type nitride semiconductor layer) 1, an active layer 3, and asecond conductive type semiconductor layer (p-type nitride semiconductorlayer) 2 are laminated on a substrate 12 and, by providing a resonatorend on both ends vertical to a longitudinal direction on a stripe, awaveguide region is formed in which a stripe direction is a directingdirection (resonating direction). One of resonator ends is a lightemitting side resonator end (light emitting plane) having the functionof mainly emitting the light to the outside, and the other is a lightreflection side resonator end (monitor end) having the function ofmainly reflecting the light in a waveguide region. A first insulatingmembrane 10 is formed on a side of a stripe-like convex part (ridge) 8and on an upper plane of a laminate structure continuing to this side. Astripe-like p-side ohmic electrode 5 which is ohmic contact with ap-type nitride semiconductor layer is provided on an upper plane of aconvex part 8 of a p-type nitride semiconductor layer 2 via a firstinsulating membrane 10. In addition, in an n-type nitride semiconductorlayer which is exposed along a laminate structure, an n-side ohmicelectrode 7 which ohmic-contacts with an n-type nitride semiconductorlayer is formed in a stripe-like manner. Both electrodes are providedgenerally-parallel. On these electrodes, a second insulating membrane 11having an opening is further provided, and a p-side pad electrode 4 andan n-side pad electrode 6 are formed, respectively, so as to contactwith an ohmic electrode via this second insulating membrane 11.

[0152] In the semiconductor laser device of the present embodiment 3, byproviding a protective membrane having the light transmittance on an endin a direction vertical to a light directing direction of a waveguideregion, release of the light is controlled. In particular, by providinga first protective membrane 109 having the high light transmittance onan emitting part of a resonator plane on an emitting side, deteriorationof a resonator plane is prevented and, at the same time, the laser lightis easily emitted. In addition, by providing a second protectivemembrane 110 having the lower light transmittance than that of a firstprotective membrane 109 on both sides of an emitting part in a resonatorplane on an emitting side, stray light is not released from the vicinityof an emitting plane. Thereby, in the semiconductor laser device of thepresent embodiment 3, stray light release of stray light to the outsidecan be prevented and occurrence of a ripple can be suppressed.

[0153] In the thus structured laser device of an embodiment 3, the lightgenerated from a light emitting region containing an active layer isdirected mainly in a waveguide region and emitted through an end of awaveguide region (emitting plane) in a resonator plane to become thelaser light (main beam). However, when a resonator plane on an emittingside is exposed, the emitting plane is easily deteriorated at highoutput and COD is easily produced. In addition, a part of the light isexuded from a waveguide region to become stray light which istransmitted in a device and released through parts other than anemitting plane to the outside. Overlapping of this with a main beamgenerates a ripple. Here, the light, stray light which is released tothe outside is the light transmitted to a device end at an angle atwhich total reflection does not occurs. The totally reflected straylight is reflected again toward the inside of a device and reflection isrepeated in a device until it reaches an end at a total reflectionangle. During repetition of reflection, stray light is resonated andamplified. Then, when this amplified stray light is released to theoutside, it is mixed in a main beam to generate a ripple. By forming twoprotective membranes having the different light transmittance on an endas in the present embodiment 3, emission of the light can be controlled(the light emitted through parts other than an emitting plane can besuppressed).

[0154] In the semiconductor laser device of the present embodiment 3,all or a part of respective protective membranes may be overlapped at aposition where two protective membranes having the differenttransmittance are contacted. By protecting second protective membranes110 on both sides of an emitting plane in a resonator plane as in FIG.14A and providing a first protective membrane 109 so as to cover it asin FIG. 14B, a structure is obtained in which only a first protective109 is formed on an emitting plane and a first protective membrane 109is laminated on a second protective membrane 110 on both sides of anemitting plane (in the vicinity of an emitting plane). In addition, inthe present invention, an end structure on an emitting side isstructured as in an embodiment 1 and, as shown in FIG. 17B, a firstprotective membrane 109 may be provided on a wide range of a resonatingend, a non-resonating end and whole end side of a second side, and asecond protective membrane 110 may be provided thereon except for aresonator end.

[0155] Like this, if a part where a first protective membrane 109 andsecond protective membrane 110 are overlapped is a part other than anemitting plane on an emitting side, any one of the protective membrane109 and the second protective membrane 110 may be formed first.Preferable order can be selected for formation, depending on a materialfor a protective membrane and the like. In addition, by formation byoverlapping, formation can be performed so that a semiconductor layer isnot exposed at the boundary.

[0156] In addition, in the present invention, as shown in FIG. 15, afirst protective membrane 109 and a second protective membrane 110 canbe made not to be overlapped with each other. By such the provision, adifference in respective light transmittances can be effectivelyutilized and, by no overlapping part, since a thickness of a membranedoes not grow large, a main beam becomes difficult to be physicallyblocked.

[0157] In addition, an end may be formed in which neither a firstprotective membrane 109 nor a second protective membrane 110 isprovided. In the case where a protective membrane is formed and,thereafter, it is divided and an end appears depending on a step, forexample, as in FIG. 16, neither of protective membranes is not formed onan end of a substrate 12. However, since it is isolated from a partthrough which the laser light is emitted, there is no problem.

[0158] In addition, when a ripple of the laser light emitted through aresonator plane is small, a first protective membrane 109 having thehigh light transmittance may be provided on a resonator plane on anemitting side, a second protective membrane 110 which is the same as thefirst protective membrane 109 may be used.

[0159] As described above, in the present embodiment 3, by providing twoprotective membranes having the different light transmittance on an endof a resonator plane, a light emitting part is limited to a prescribedrange to control release and, thus, better FFP can be stably obtained.In the present embodiment 3, better FFP can be stably obtained withoutprocessing a device itself as in an embodiment 1 and without influencingon the beam properties.

EMBODIMENT 4

[0160] As shown in FIG. 17A, FIG. 17B, FIG. 18A and FIG. 18B, thesemiconductor laser device of the present embodiment 4 is obtained yapplying a first protective membrane 109 and a second protectivemembrane 110 of an embodiment 3 to a semiconductor laser device havingthe same end structure as that explained for an embodiment 2, in whichboth sides of a resonator end are removed below an active layer in thevicinity of a light emitting side resonator plane and a corner part of alaminate structure is removed. That is, in the semiconductor laserdevice of an embodiment 4, an end in a direction vertical to a lightdirecting direction of a stripe-like waveguide region of a laminatestructure is not a single plane, and is composed of a resonator endwhich is a light emitting plane, and a non-resonator end which issituated on a plane different from the resonator end. In addition, evenwhen seen from a plane (side) parallel with a light directing directionof a stripe-like waveguide region of a laminate structure, a first sidehaving an active layer cross-section isolated from a waveguide region,and a second side having an active layer cross-section which is situatedat a position nearer a waveguide region, are formed. And, a firstprotective membrane 109 is provided on a resonator plane which is anemitting plane (FIG. 17B) and, at the same time, a second protectivemembrane 110 is provided on a non-resonator plane and a second side(FIG. 17A). Specifically, at least a second protective membrane 110 isprovided on a non-resonator plane containing an active layercross-section which is not on the same plane as a resonator end, and ona second side nearer a waveguide region, and a first protective membrane109 is provided so as to cover both of a resonator end and a secondprotective membrane 110.

[0161] Like this, in the present embodiment 4, a second protectivemembrane having the low light transmittance is provided on a second sidenear a waveguide region and on a non-resonating end, whereby, the lightis difficult to be released, and a first protective membrane having thehigh light transmittance is formed on a resonator plane on an emittingside, whereby, the laser light is effectively emitted and, at the sametime, release of stray light is prevented.

[0162] In addition, in the semiconductor laser device of the presentembodiment 4, by limiting a width of an active layer on an emitting sideas in an embodiment 1, the beam properties can be also improved. In thepresent embodiment 4, since processing of a device itself is necessarybefore first and second protective membranes are provided on the surfaceof a device, the workability is superior in an embodiment 3. However, abeam having a wide divergence angle can be obtained by controlling awidth of an active layer and, thus, the beam properties can be improved,leading to the advantage which is not harbored by an embodiment 3.Further, since a second protective membrane 110 can be provided in frontof a resonator plane, a ripple can be more effectively reduced.

[0163] In addition, as in an embodiment 1, the semiconductor laserdevice of the present embodiment 4 may be formed so that a side wall(side) of a ridge and a second side are on the same plane. However, whena ridge is thinly formed, since it becomes difficult to confine thelight in a width of the ridge and the better properties can not beobtained, it is preferable that a second side is formed so that a widthof an active layer is larger than that of a stripe-like convex part(ridge) as in FIG. 17 and FIG. 18. In addition, since the strength canbe enhanced by rendering a width of an active layer of an end on anemitting side larger than that of a ridge, breakage hardly occurs and aresonator plane can be stably formed. In particular, in the case where awidth of a ridge is formed narrowly, when a width of an active layercross-section exposed on an emitting plane is made narrow correspondingto a width of a ridge, a resonator plane is not cleaved at a desiredposition but is broken when the plane is formed by cleavage. However, byexposing an active layer cross-section having a larger width than thatof a ridge on an emitting plane, a resonator plane can be stablycleaved.

[0164] In the case where a second protective membrane in the presentinvention is applied to an end structure in which both of a resonatorend and a second side are provided, when the protective membrane isprovided on both, the protective membrane is effective. However, theprotective membrane may be provided only on one of them, or it may beprovided continuously. In addition, a second protective membrane may beformed on a plane (slant face) which is formed over a resonator end anda first side.

[0165] In addition, a non-resonator plane and a second side may bevariously changed as explained in an embodiment 1.

[0166] In addition, it is enough that a second protective membrane isprovided so as to cover at least a layer through which the light istransmitted. Therefore, it may be provided so as to cover at least anactive layer, and it may not be formed on the whole plane containing anactive layer. It is preferable that a second protective membrane isprovided also in a layer through which the light is easily transmitteddue to formation of a guiding layer and the like.

[0167] A preferable material for a first protective membrane 109 and asecond protective membrane 110 in embodiments 3 and 4 will be describedbelow.

[0168] As a material used in a first protective membrane and a secondprotective membrane, any one of a conductor, a semiconductor and aninsulator may be used. However, when a conductor is used, it isnecessary that a conductor is provided so as not to contact-directlywith an electrode, in order to prevent short circuit and in order not toblock the current flow in a device structure. In addition, when asemiconductor is used, a first protective membrane having a larger bandgap than that of an active layer is preferable. In addition, it ispreferable to use a second protective membrane having a smaller band gapthan that of an active layer. The most preferable materials among thesematerials can be selected depending on a structure of a device, amanufacturing step, a manufacturing process and the like.

[0169] In addition, as a first protective membrane, a dielectricmulti-layered membrane may be used. Thereby, the function of allowingthe light to be easily transmitted and protecting an exposed end, inparticular, an active layer is accompanied therewith.

[0170] In addition, as a specific material used in a first protectivemembrane and a second protective membrane, there are materials describedbelow. Among them, a material having the higher light transmittance isused as a first protective membrane, and a material having the lowerlight transmittance than that of a first protective membrane is used asa second protective membrane. However, since first and second protectivemembranes are selected by comparing the light transmittances of them, amaterial for a first protective membrane is used as a second protectivemembrane in some cases by combining with another material, depending ona selected material.

[0171] That is, it goes without saying that a part through which thelaser light is mainly emitted is an end of a waveguide region. In thepresent specification, this end of a waveguide region is used as anemitting plane or an emitting part. For example, in an embodiment 1, aresonator end itself with a limited width is an emitting plane. However,when an emitting side end is composed of a single plane as in anembodiment 3, a part which is to be an end of a waveguide region amongthe single plane is an emitting part or an emitting plane.

[0172] In contrast to the laser light which is radiated through thisemitting part, the light which is radiated though parts other than anemitting part is the light having the adverse effect on a shape of alaser beam, and has the extremely small intensity as compared with thelight which is radiated through an emitting part. Therefore, simply byrendering the transmittance of a second protective membrane slightlysmaller as compared with the transmittance of a first protectivemembrane, the light which is radiated through parts other than anemitting part is significantly reduced, and the adverse effect on ashape of a laser beam is suppressed.

[0173] Therefore, in the laser devices in embodiments 3 and 4, asmaterials for a first protective membrane and a second protectivemembrane, various materials can be selected at least under the conditionthat the transmittance of a first protective membrane is larger than thetransmittance of a second protective membrane.

[0174] (First Protective Membrane)

[0175] As a preferable material for a first protective membrane, any oneselected from compounds such as oxides, nitrides and fluorides of Si,Mg, Al, Hf, Nb, Zr, Sc, Ta, Ga, Zn, Y, B and Ti, or a multi-layeredmembrane composed of them can be used. These may be used alone, or maybe used in combination thereof. A preferable material includes materialsusing Si, Mg, Al, Hf, Zr, Y and Ga. In addition, as a semiconductormaterial, AlN, AlGaN and BN can be used. As an insulating material,compounds such as oxides, nitrides, fluorides and the like of Si, Mg,Al, Hf, Nb, Zr, Sc, Ta, Ga, Zn, Y and B can be used.

[0176] In addition, by structuring a first protective membrane with amaterial having the refractive index between the refractive index of theair and the refractive index of a semiconductor, the membrane can beused as an anti-reflection (AR) membrane and, thus, reflection of thelight can be prevented. When used as an AR membrane, it is suitable thatthe relationship between the refractive index n_(AR) of a firstprotective membrane and the refractive index n_(s) of a semiconductordevice which is a laminate structure satisfies: 0.75 n_(s)^(1/2)≦n_(AR)≦1.25 n_(s) ^(1/2). Preferably, 0.85 n_(s)^(1/2)≦n_(AR)≦1.15 n_(s) ^(1/2), most preferably 0.93 n_(s)^(1/2)≦n_(AR)≦1.07. As a material having such the refractive index,there are Al₂O₃, MgO, Y₂O₃, SiO₂, MgF₂ and the like. The AR membrane isobtained by these materials and controlling a thickness thereof. Inorder to obtain the AR membrane, a thickness preferably satisfies thecondition: λ×(2 m_(AR)−1)/4 n_(AR), or λ×m_(AR)/2 n+λ×(2 m_(AR)−1)/4n_(AR) (m_(AR)=1, 2, 3, . . . ), more preferably the thickness isλ/4n_(AR), orλ/2 n+λ/4 n_(AR) (λ: wavelength of the light generated from anactive layer). By forming a protective membrane so as to satisfy suchthe condition, the AR membrane can be easily obtained.

[0177] In addition, when a conductive material such as metal materialsis used, an insulating layer may be formed on the surface of a laminatestructure, and the material may be formed on the insulating layer.Thereby, even a material having the poor adherability with a laminatestructure can be used as a material for a first protective membrane.

[0178] In addition, when the present invention focuses on protection ofan emitting plane, it is preferable that a first protective membrane isstructured using a material having a refractive index difference whichis within ±10% of the refractive index of a laminate structure. Inaddition, by forming a first protective membrane of a material havingthe refractive index near that of a semiconductor layer (mainly activelayer) constituting a waveguide region, a membrane (absent layer) inwhich the reflectivity and the transmittance of the light are notchanged even when a thickness of a first protective membrane is changedmore or less.

[0179] For example, when a laminate structure is a nitride semiconductordevice, the refractive index of an active layer in which a wavelength isset to be about 400 nm is about 2.5 (provided that, actually, therefractive index varies more or less depending on the concentration ofthe impurity and a constituent ratio). In this case, a preferablerefractive index of a first protective membrane is ±10%. of 2.5, being2.25 to 2.75. Specific examples of a material having the refractiveindex in this range include Nb₂O₅ and the like. When the refractiveindex is within ±10% of that of a laminate structure, a laminatestructure can be protected while the properties of the emitted light arescarcely changed. A material having the refractive index which is higherthan 10% of that of a laminate structure can reduce a threshold butdeteriorates the slope efficacy. On the other hand, a material havingthe refractive index which is lower than the 10% improves the slopeefficacy but increases a threshold, being not preferable.

[0180] Here, electric field intensity distributions in the case of wherea first protective membrane is not formed on an emitting plane of aresonator plane and the case where the protective membrane is formed,are shown in FIGS. 19A to 19C. As a laminate structure, a semiconductordevice comprising gallium nitride (GaN) is used. FIG. 19A shows the casewhere a protective membrane is not formed, FIG. 19B shows the case whereAl₂O₃ is formed mainly for the purpose of preventing reflection, andFIG. 19C shows the case where Nb₂O₅ is formed mainly for the purpose ofprotecting an emitting end. In addition, a broken line shows arefractive index distribution, and a solid line shows the electric fieldintensity light power distribution).

[0181] As seen from FIG. 19A, when a first protective membrane is notformed, the electric field intensity is maximum at a device end. This isbecause a device end is contacted with a layer having the low refractiveindex (air layer: refractive index 1). In such the case, the electricfield intensity becomes maximum at the interface. For this reason, anexcess load is applied to a resonator plane and, as a result, therearises a problem that COD easily occurs.

[0182] To the contrary, when Al₂O₃ is formed as a first protectivemembrane, in the electric field intensity, a load applied to a deviceend is smaller as compared with the case where a first protectivemembrane is not formed, as shown in FIG. 19B. Such the protectivemembrane can reduce a load applied to a resonator plane by controlling athickness so as to be an AR membrane. Conversely, there arises thephenomenon that RIN (relative intensity of noise) properties aredeteriorated and the noise is slightly increased. For this reason, suchthe device can be used for a particular utility where influence of IRNis small, such as high output utility.

[0183] In addition, when Nb₂O₅ is used as a first protective membrane tobe formed on a resonator plane, since the electric field intensity at adevice end can be lowered as shown in FIG. 19C, a load applied to an endcan be suppressed to prevent deterioration. In addition, Nb₂O₅ hasalmost the same refractive index as that of GaN, the reflectivity of anend (surface of a first protective membrane) is not lowered as in Al₂O₃and, thus, deterioration of the RIN properties can be prevented. Forthis reason, it is preferable that such the device is used in utilityattaching greater importance to the safety, e.g., the fields dealingoptical disc such as DVR.

[0184] In addition, since a protective membrane has various propertiesdepending on a refractive index and a thickness, it is preferable that athickness of a first protective membrane isλ/4 n or odd-fold of thesame. Thereby, damage applied to a resonator plane can be reduced. Asdescribed above, by taking this and the refractive index intoconsideration, an AR membrane can be obtained. However, it is preferablethat a thickness is λ/4 n irrespective of the refractive index. In thecase of a single layer, a thickness may be λ/4 n and, in the case of amulti-layered membrane, a thickness may be λ/2 n+λ/4 n or realnumber-fold of the same. Thereby, since such a thickness is obtainedthat the electric field intensity of a standing wave takes a minimum atthe interface between a laminate structure end and a protective membrane(see FIG. 19C), damage to a resonator end can be suppressed, and thedevice life can be improved.

[0185] Described above, control of a thickness of a protective membranecan be applied not only to a resonator plane on a light emitting sidebut also to a protective membrane (mirror) formed on a light reflectingside (monitor side). For emission of the laser light, since theproperties are deteriorated even when one of resonators is deteriorated,deterioration can be prevented and the device life can be improved bycontrolling a thickness of a protective membrane (mirror) so that adevice does not undergo damage due to the light from an active layeralso on a light reflecting side, as in a light emitting side.

[0186] (Second Protective Membrane)

[0187] As a material for a second protective membrane, there arematerials using Ni, Cr, Ti, Cu, Fe, Zr, Hf, Nb, W, Rh, Ru, Mg, Ga, Pt,Au, Si, Pd, V, Ta, Mo, C and the like, more preferable are materialsusing Ni, Cr, Ti and Si. In addition, as a semiconductor material, Si,InGaN, GaAs and InP can be used. As an insulating material, TiO₂ andCrO₂ can be used. It is preferable that, a shading membrane throughwhich the light is hardly transmitted is formed using these materials.As a specific preferable material, Ti, TiO₂, SiO₂, RhO and ZrO₂ arepreferable, and these may be formed as a single-layered membrane or amulti-layered membrane. In order to form these at a desired position,various methods such as vapor deposition, sputtering and the like can beused.

[0188] Herein, in the present invention, the light transmittance is arelative value relative to the output of the laser light emitted from awaveguide region when a protective membrane is not formed, and thehigher value shows the higher light transmittance. In addition, when thelight transmittance is almost 0% and the light is almost blocked, it isregarded as a shading membrane. This light transmittance varies even inthe same material, depending on a thickness. In addition, even in thedifferent refractive index, the light transmittance becomes almost thesame magnitude from a balance between a thickness, in some cases.

[0189] In addition, a thickness of a second protective membrane variesdepending on a material, but it is preferably 200 Å or more when aconductive material is used. This second protective membrane is amembrane allowing the light to be emitted to the outside with difficultyand, therefore, an object can be easily attained when a thickness ismade to be large. However, in order not to block the light emitted froman emitting plane and in order to block the light, a thickness ispreferably around 1500 Å to 3000 521 . However, when a conductivematerial is used as a second protective membrane, it is necessary thatan insulating membrane is formed between a device and a secondprotective membrane. In this case, a thickness of an insulating membranedoes not matter as long as the insulating property can be maintained. Inaddition, the light transmittance does not particularly matter. Inaddition, when a dielectric multi-layered membrane is used as a secondprotective membrane, the light transmittance can be controlled byforming a membrane having the low refractive index at a thickness of λ/4n and forming a membrane having the high refractive index thereon at athickness of λ/4 n.

[0190] In addition, as a preferable combination of a first protectivemembrane and a second protective membrane, Nb₂O₅ is used as a firstprotective membrane on an emitting plane of a resonator plane, and ashading membrane is used as a second protective membrane in the vicinityof a resonator plane except for an emitting plane. As a shadingmembrane, metal materials and compounds thereof are preferable. As aspecific material, Ti, TiO₂, SiO₂, RhO and ZrO₂ are preferable, andthese may be formed as a single-layered membrane or a multi-layeredmembrane. By selecting such the materials, a semiconductor laser devicewhich suppresses deterioration of a resonator plane and has littleripple can be obtained.

[0191] A waveguide region can be formed according to the same manner asthat for an embodiment 1 and the like.

[0192] In addition, in order to adopt a longitudinal direction of astripe-like convex part as a resonating direction, a pair of resonatorplanes provided on an end are a flat plane formed by cleavage oretching. A method for forming a resonator plane varies depending on akind of a substrate described later. When the same kind of substratesare used, for example, when a laminate structure comprising a galliumnitride series compound semiconductor layer is formed on a galliumnitride substrate, a resonator plane can be easily formed by cleavage.However, when a laminate structure is formed on different substrates,for example, when a gallium nitride series compound semiconductor layeris formed on a sapphire substrate, a cleavage plane for a substrate isnot consistent with a cleavage plane for a semiconductor layer thereondepending on a main plane of a substrate, and a resonator plane ishardly obtained. In such the case, it is preferable that a resonatorplane is formed by etching. In addition, when a resonator plane isformed by etching, if etched deep until a substrate is exposed, a planeis roughened in some cases and, therefore, a better resonator plane isobtained by etching to a depth at which at least a waveguide region isexposed. However, in order to make division of a device easy, it ispreferable to etch until a substrate is exposed. However, when an end isprocessed by etching, an end of a single plane is not obtained as in acleaved resonator plane, and a difference in level is generated as inFIG. 14. In particular, since increase in etching time increases adifference in level to that extent and, in that case, it is necessarythat a part protruding more than a resonator plane does not block theemitted light. In addition, both of resonator planes may be formed bythe same method such as cleavage and etching, or may be formed by adifferent method. For example, one of them is cleaved and the other isetched. The method can be appropriately selected depending on an object.

[0193] In addition, a stripe-like convex part can be formed according tothe same manner as that for an embodiment 1 and the like, varioussubstrates shown in embodiments 1 to 3 can be applied.

[0194] Further, various kinds of laminate structures and semiconductorlayers constituting the structures explained in an embodiment 1 and thelike can be used.

[0195] Still further, when the same structure on an emitting end sidefor an embodiment 1 is applied, a method for forming a non-resonatorplane and a second side explained in embodiments 1 to 3 can be applied.

EXAMPLES

[0196] In the present invention, as a structure of each layer of a firstconductive type semiconductor layer, an active layer and a secondconductive type semiconductor layer which constitute a laminatestructure, various layer structures can be used. As a specific structureof a device, for example, there are device structures described inexamples below. In addition, an electrode, an insulating membrane(protective membrane) and the like are not particularly limited, butvarious ones can be used. In the case of a nitride semiconductor laserdevice, as a method for growing a nitride semiconductor, all the knownmethods for growing a nitride semiconductor can be used, such as MOVPE,MOCVD (metal organic chemical vapor deposition), HVPE (halide vaporphase epitaxy), MBE (molecular beam epitaxy) and the like.

[0197] A semiconductor laser device using a nitride semiconductor willbe explained below, but it goes without saying that the semiconductorlaser device of the present invention is not limited thereto and can beapplied to various laser devices in the technical concept of the presentinvention.

Example 1

[0198] In an example 1, a heterogeneous substrate different from anitride semiconductor is used as a substrate. However, in the presentinvention, a substrate comprising a nitride semiconductor such as a GaNsubstrate may be used. Here, as a heterogeneous substrate, for example,substrate materials which can grow a nitride semiconductor can be used,such as sapphire, spinel, ZnS, ZnO, GaAs, Si and SiC having either of Cplane, R plane and A plane as a main plane, oxide substrates which arelattice-matched with a nitride semiconductor, and the like. Preferableexamples of a heterogeneous substrate include sapphire and spinel. Inaddition, a heterogeneous substrate may be off angle and, in this case,when step-wisely off angled substrate is used, growth of a ground layercomprising gallium nitride can be performed with the bettercrystallinity, being preferable. Further, when a heterogeneous substrateis used, a device structure having a single substance substrate of anitride semiconductor may be formed by growing a nitride semiconductorwhich is to be a ground layer before formation of a device structure, ona heterogeneous substrate and, thereafter, removing a heterogeneoussubstrate by a method such as grinding, or alternatively, aheterogeneous substrate may be removed after formation of a devicestructure. In the case where a heterogeneous substrate is used, when adevice is formed via a buffer layer and a ground layer, a nitridesemiconductor having the better crystallinity can be grown.

[0199] A semiconductor laser device of the example 1 will be explainedbelow in a manufacturing step order.

[0200] (Buffer Layer)

[0201] A two inch φ heterogeneous substrate comprising sapphire having aC plane as a main plane is set in a MOVPE reactor, a temperature is setat 500°C., and a buffer layer comprising GaN is grown at a thickness of200 Å using trimethylgallium (TMG) and ammonia (NH₃).

[0202] (Ground Layer)

[0203] After formation of a buffer layer, a temperature is set at 1050°C., and a nitride semiconductor layer comprising undoped GaN is grown ata thickness of 4 μm using TMG and ammonia. This layer acts as a groundlayer (growth substrate) in growing each layer which forms a devicestructure. Besides, when a nitride semiconductor grown by ELOG(Epitaxially Laterally Overgrowth) is used as a growth substrate, aground layer (growth substrate) having the better crystallinity isobtained. As a specific example of the ELOG-grown layer, there is thefollowing method.

EMBODIMENT 1 OF ELOG-GROWN LAYER

[0204] A nitride semiconductor layer is grown on a heterogeneoussubstrate, and a protective membrane comprising a material (on thesurface of which a nitride semiconductor is not grown at all or hardlygrown) is provided in a stripe-like manner so that openings are formedat a constant interval. A mask region in which a mask is formed likethis, and a non-mask region in which the surface of a nitridesemiconductor is exposed for growing a nitride semiconductor, areprovided alternately and, by growing a nitride semiconductor startingfrom the non-mask region to perform lateral growth so as to cover a maskin addition to growth in a thickness direction, a nitride semiconductoris grown also on a mask region to form a membrane so as to cover thewhole.

EMBODIMENT 2 OF ELOG-GROWN LAYER

[0205] Openings are provided at a constant interval on a nitridesemiconductor layer grown on a heterogeneous substrate, and a nitridesemiconductor is grown laterally starting from a nitride semiconductoron the opening side, to a nitride semiconductor layer which covers thewhole.

[0206] Next, each layer constituting a laminate structure is formed on aground layer comprising a nitride semiconductor.

[0207] (N-Type Contact Layer)

[0208] An n-type contact layer comprising GaN doped with Si at1×10¹⁸/cm³ is grown at a thickness of 4.5 μm at 1050° C. on a groundlayer (nitride semiconductor substrate) using TMG, ammonia, and a silanegas as an impurity gas.

[0209] (Crack Preventing Layer)

[0210] Then, a temperature is set at 800° C., and a crack preventinglayer comprising In_(0.06)Ga_(0.94)N is grown at a thickness of 0.15 μmusing TMG, TMI (trimethylindium) and ammonia. This crack preventinglayer may be omitted.

[0211] (N-Type Cladding Layer)

[0212] Then, a temperature is set at 1050° C., an A layer comprisingundoped AlGaN is grown at a thickness of 25 A using TMA(trimethylaluminium), TMG and ammonia as a raw material gas,subsequently TMA is stopped, and a B layer comprising GaN doped with Siat 5×10¹⁸/cm³ is grown at a thickness of 25 A using a silane gas as animpurity gas. These procedures are repeated 160 times, respectively, tolaminate an A layer and a B layer alternately, and an n-type claddinglayer comprising a multi-layered membrane (superlattice structure)having a total thickness of 8000 Å is grown. Upon this, when a crystalmixing ratio of Al for undoped AlGaN is in a range of not less than 0.05and not more than 0.3, a difference in refractive index whichsufficiently functions as a cladding layer can be set.

[0213] (N-Type Light Guiding Layer)

[0214] Then, an n-type light guiding layer comprising undoped GaN isgrown at a thickness of 0.1 μm at the same temperature using TMG andammonia as a raw material gas. This layer may be doped with an n-typeimpurity.

[0215] (Active Layer)

[0216] Then, a temperature is set at 800° C., and a barrier layercomprising In_(0.05)Ga_(0.95)N doped with Si at 5×10¹⁸/cm³ is grown at athickness of 100 Å using TMI (trimethylindium), TMG and ammonia as a rawmaterial, and a silane gas as an impurity gas. Subsequently, a silanegas is stopped, and a well layer comprising undoped In_(0.1)Ga_(0.9)N isgrown at a thickness of 50 Å. These procedures are repeated three timesand, finally, a barrier layer is laminated to grow an active layer of amultiple quantum well structure (MQW) having a total thickness of 550 Å.

[0217] (P-Type Cap Layer)

[0218] Then, a p-type electron confining layer comprising AlGaN dopedwith Mg at 1×10¹⁹/cm³ is grown at a thickness of 100 Å at the sametemperature using TMA, TMG and ammonia as a raw material, and Cp₂Mg(cyclopentadienylmagnesium) as an impurity gas.

[0219] (P-Type Light Guiding Layer)

[0220] Then, a temperature is set at 1050° C., and a p-type lightguiding layer comprising undoped GaN is grown at a thickness of 750 Åusing TMG and ammonia as a raw material gas. This p-type light guidinglayer is grown undoped, but may be doped with Mg.

[0221] (P-Type Cladding Layer)

[0222] Subsequently, a layer comprising undoped Al_(0.6)Ga_(0.84)N isgrown at a thickness of 25 A at 1050° C., TMG is stopped, and a layercomprising Mg-doped GaN is grown at a thickness of 25 A using Cp₂Mg, togrow a p-type cladding layer of a superlattice layer having a totalthickness of 0.6 μm. At least one of p-type cladding layers contains anitride semiconductor layer containing Al and, when a layer is preparedwith a superlattice in which nitride semiconductor layers, each havingthe different band gap energy, all the impurities are doped more intoone of the layers and, there is a tendency that the crystallinitybecomes better when so-called modified doping is performed, but both maybe doped similarly.

[0223] (P-Type Contact Layer)

[0224] Finally, a p-type contact layer comprising p-type GaN doped withMg at 1×10²⁰/cm³ is grown on a p-type cladding layer at a thickness of150 Å at 1050° C. A p-type contact layer can be structured with p-typeIn_(x)Al_(y)Ga_(1−x−y)N(x≦0, y≦0, X+Y≦1) and, preferably by forming GaNdoped with Mg, most preferable ohmic contact with a p-electrode isobtained. After completion of the reaction, a wafer is annealed at 700°C. under the nitrogen atmosphere in a reactor to further reduce theresistance of a p-type layer.

[0225] (Exposure of an n-Type Layer)

[0226] After a laminate structure is formed by growing a nitridesemiconductor as described above, a wafer is removed from a reactor, anda protective membrane comprising SiO₂ is formed on the surface of anuppermost layer p-type contact layer, which is etched with a SiCl₄ gasusing RIE (reactive ion etching), to expose the surface of an n-typecontact layer on which an n-electrode is to be formed. Upon this, anactive layer end which is to be a resonator plane is exposed, and anetching end may be used as a resonator plane. Instead of SiCl₄ gas, Cl₂gas may be used as a etching gas.

[0227] (Formation of a Stripe-Like Convex Part and a Shading LayerForming Plane)

[0228] Then, in order to form a stripe-like waveguide region, after aprotective membrane comprising Si oxide (mainly SiO₂) is formed onalmost the whole plane of an uppermost layer p-type contact layer at athickness of 0.5 μm using a CVD apparatus, a mask having a prescribedshape is formed on a protective membrane, and a stripe-like protectivemembrane is formed by the photolithography technique using a CHF₃ gas inthe RIE apparatus, to form a stripe-like convex part above an activelayer. Thereafter, only the vicinity of a resonator plane of this convexpart is further etched to below an active layer using a resist mask toremove a corner part of a device as in FIG. 1 and, thus, a non-resonatorplane which is a shading layer forming plane, and a second side areformed.

[0229] (Light Non-Transmittable Layer)

[0230] A shading layer continuing to a light non-resonator plane, asecond side and an exposed plane of an n-type layer is formed bysputtering while the aforementioned protective membrane and resist maskare retained. A shading layer comprises Si, and a thickness thereof is4000 Å. This shading layer may be formed after a first insulating layeris formed in a post-step. Alternatively, the layer may be formed afteran ohmic electrode is formed and a second insulating membrane is formed.

[0231] (First Insulating Membrane)

[0232] A first insulating membrane comprising ZrO₂ is formed on thesurface of a p-type layer while the SiO₂ mask is retained. This firstinsulating membrane may be provided on the whole semiconductor layer bymasking an n-side ohmic electrode forming plane. In addition, a part onwhich no insulating membrane is formed is provided for later easydivision. This part is provided in a 10 μm stripe-like manner so as tobe orthogonal with a convex part. A first insulating membrane is formed,which is soaked in a buffered solution to dissolve and remove SiO₂formed on an upper plane of a stripe-like convex part, and ZrO₂ on ap-type contact layer (further on an n-type contact layer) is removedtogether with SiO₂ by a liftoff method. Thereby, an upper plane of astripe-like convex part is exposed and, thus, a side of a convex partbecomes a structure covered with ZrO₂.

[0233] (Ohmic Electrode)

[0234] Then, a p-side ohmic electrode is formed on a first insulatingmembrane on the most superficial convex part on a p-type contact layer.This p-side ohmic electrode comprises Au and Ni. In addition, astripe-like n-side ohmic electrode is formed also on the surface of ann-type contact layer which is exposed by etching. An n-side ohmicelectrode comprises Ti and Al. After formation of them, each is annealedat 600° C. in the atmosphere at a ratio of oxygen:nitrogen of 80:20, toalloy ohmic electrodes on both p-side and n-side and, thus, the betterohmic properties are obtained.

[0235] (Second Insulating Membrane)

[0236] Then, a resist is coated on a part of a p-side ohmic electrodeand an n-side ohmic electrode on a stripe-like convex part and a secondinsulating membrane comprising Si oxide (mainly SiO₂) is formed on thewhole plane, which is lifted off to expose a part of a p-side ohmicelectrode and an n-side ohmic electrode. A division position is aposition which is situated between previously formed non-resonatorplanes so as to confront each other and is orthogonal with a stripe-likeconvex part. A device is divided by cleaving this part. By not formingfirst and second insulating membranes and electrodes in a stripe-likerange of a width of around 10 μm which holds this division position, itbecomes easy to perform cleavage and convert a resonator plane into amirror plane.

[0237] (Pad Electrode)

[0238] Then, a p-side pad electrode and an n-side pad electrode areformed, respectively, so as to cover the aforementioned insulatingmembrane. The electrodes comprise Ni—Ti—Au. This pad electrode is incontact with an exposed ohmic electrode in a stripe-like manner.

[0239] (Cleavage and Resonator Plane Formation)

[0240] A sapphire substrate of a wafer is abraded to 70 μm, which iscleaved in a bar-like manner starting from a substrate side in adirection vertical to a stripe-like electrode, to form a resonator planeon a cleavage plane (11-00 plane, plane corresponding to a side of ahexagonal pillar crystal=M plane). This resonator plane may be formed byetching.

[0241] (Mirror Formation)

[0242] On the thus formed resonator plane, a dielectric multi-layeredmembrane comprising SiO₂ and ZrO₂ is formed as a mirror. A protectivemembrane comprising ZrO₂ is formed on a resonator plane on a lightreflecting side using a sputtering apparatus and, then, SiO₂ and ZrO₂are alternately laminated at three pairs to form a high reflectingmembrane. Here, a thickness of a protective membrane, and thicknesses ofSiO₂ membrane and ZrO₂ membrane constituting a high reflecting membranecan be set to a preferable thickness, respectively, depending on anemitting wavelength from an active layer. In addition, nothing may beprovided on a resonator plane on a light emitting side, or a first lowreflecting membrane comprising ZrO₂ and a second low reflecting membranecomprising SiO₂ may be formed thereon using a sputtering apparatus. Uponthis, a mirror may be formed on a non-resonator plane. Then, a bar isfinally cut in a direction parallel with a stripe-like convex part toobtain a semiconductor laser device of the present invention.

[0243] In the thus obtained semiconductor laser device, continuousoscillation of an oscillation wavelength 405 nm was confirmed at roomtemperature and at a threshold 2.0 kA/cm² and a high output 30 mW. Inaddition, in FFP, the better beam free of ripple was obtained.

Example 2

[0244] In an example 1, a nitride semiconductor substrate comprising GaNwhich is formed on sapphire (prepared as below) is used as a substrate.First, a two inch (p sapphire substrate having a thickness of 425 μm, aC plane as a main plane and an A plane as an orientation flat plane(hereinafter, referred to as orifla plane) is prepared as aheterogeneous substrate on which a nitride semiconductor is to be grown,and the substrate (wafer) is set in a reactor for MOCVD. Then, atemperature is set at 510° C., and a low temperature-grown buffer layercomprising GaN is grown on a sapphire substrate at a thickness of about200 Å using hydrogen as a carrier gas, and ammonia and TNG(trimethylgallium) as a raw material gas. Then, a temperature is set at1050° C., and a ground layer comprising undoped GaN is grown at athickness of 2.5 μm using TMG and ammonia as a raw material gas.Subsequently, a plurality of stripe-like masks comprising SiO₂ having awidth of 6 μm are formed parallel in a direction that this wafer istilted from a direction vertical to an orifla plane (A plane) of asapphire substrate by θ=0.3°, so that a distance between masks (maskopening) becomes 14 μm. Then, it is returned to the MOCVD apparatus, andundoped GaN is grown at a thickness of 15 μm. Thereby, GaN selectivelygrown starting with a mask opening is grown mainly in a longitudinaldirection (thickness direction) at a mask opening, and is grown in atransverse direction on a mask and, thus, a ground layer covering a maskand a mask opening is formed (ELOG growth). In the thus grown groundlayer, a nitride semiconductor layer grown in a transverse direction canreduce penetration rearrangement. Specifically, in penetrationrearrangement, the rearrangement density becomes higher to around10¹⁰/cm² on a mask opening and at an around mask central part wherenitride semiconductors grown transversely from both sides of a mask areconnected, and the rearrangement density becomes lower to around 10⁸/cm²on a mask except for a mask central part.

[0245] (Thick Layer)

[0246] A substrate having the thus obtained nitride semiconductor isused and, subsequently, a wafer is placed in the HVPE apparatus to growfurther undoped GaN on a ground layer at a thickness of about 100 μm(this layer grown at a thickness of about 100 μm is referred to as thicklayer).

[0247] (Ground Layer)

[0248] By growing a nitride semiconductor also in a transverse directionusing a stripe-like SiO₂ mask as in the ground layer upon preparation ofa nitride semiconductor substrate on a nitride semiconductor substrate,a ground layer is grown at a thickness of 15 μm.

[0249] (Formation of a Shading Layer Forming Plane)

[0250] After formation of a ground layer, the same procedures as thosein the example 1 are performed to laminate a semiconductor layer. Afterlamination to a p-side contact layer, an n-type layer exposing step isperformed, and a stripe-like convex part ridge) having a width of 1.6 μmis formed. Then, by providing a mask having a larger width of that of aridge and etching to an n-type layer upon formation of a shading formingplane, a second side can be formed on a plane different from a ridgeside. Here, by providing a mask having a width of about 7 μm (in which aridge is situated almost at its center) and etching to an n-type layernear an active layer, a resonator plane is formed in which a width of anactive layer of a resonator plane on an emitting plane is about 7 μm.The thus formed etching planes are a non-resonator plane and a secondside, both of which are used as a shading layer forming plane.

[0251] (Light Non-Transmittable Layer)

[0252] A shading layer is formed on the thus formed second side andnon-resonator plane and on an exposed plane of an n-type layer bysputtering. First, Rh oxide is formed at a thickness of 500 Å, and thesame Rh oxide is formed thereon at a thickness of 1500 Å by changing thesputtering conditions. Like this, by laminating the same material underthe different sputtering condition to form a multi-layered membrane, ashading layer excellent in the both properties of the tightness and thelight non-transmittability can be obtained. In the example 2, since themask used for forming a shading layer forming plane is used as it is, ashading layer is formed on a second side, a non-resonator plane, and anexposed plane of an n-type layer. However, even when a shading layer isprovided so as to extend to the surface of a p-type layer by changing amask, there is no problem. By formation of a shading layer also on apart of the surface (upper plane) of a p-type layer, leakage of thelight toward an upper direction can be also prevented. In addition,peeling easily occurs in some cases due to formation of an end part of ashading layer on an end and an edge of an upper plane. However, byprovision continuing to an upper plane, a shading layer can be formedwith the better tightness, and the stable beam properties can beobtained.

[0253] (Peeling of a Heterogeneous Substrate)

[0254] Thereafter, the same procedures as those in the example 1 areperformed by formation of a pad electrode and, before cleavage, a partof a sapphire substrate, a low temperature-grown buffer layer, a groundlayer and a thick layer is removed to obtain a GaN substrate. The GaNsubstrate is formed such that a thickness thereof is about 80 μm. Here,other nitride semiconductors other than GaN may be used in a thick layeraccording to HVPE. However, in the present invention, it is preferableto use GaN or AlN on which a nitride semiconductor having the bettercrystallinity and a large thickness can be easily grown. In addition, inremoval of a heterogeneous substrate and the like, a part of a thicklayer may be removed before formation of the aforementioned devicestructure, or removal may be performed at any stage after formation of awaveguide, or after formation of an electrode. In addition, by removinga heterogeneous substrate before a wafer is cut into bar-like orchip-like, upon cutting into chip-like, cutting and cleavage can beperformed using a cleavage plane (hexagonal crystal system-approximated{11-00} M plane, {1010} A plane, (0001) C plane) of a nitridesemiconductor. Then, a eutectic crystal metal comprising Ti—Pt—Au isformed on a back, which is divided in a bar-like manner starting from asubstrate side in a direction vertical to a stripe-like electrode toform a resonator plane and form a mirror on a monitor side according tothe same manner as that in the example 1 and, thus, a semiconductorlaser device of the present invention is obtained.

[0255] In the thus obtained semiconductor laser device, continuousoscillation at an oscillation wavelength 405 nm is confirmed at roomtemperature and at a threshold 2.0 kA/cm² and a high output 30 mW. Thebetter beam having no ripple in FFP can be obtained.

Example 3

[0256] In the example 2, the same procedures as those in the example 2are performed except that a substrate which is prepared as describedbelow is used. First, a buffer layer comprising GaN is grown at athickness of 200 Å at 510° C. using hydrogen as a carrier gas andammonia and TMG as a raw material gas and using a sapphire substratehaving a C plane as a main plane and an A plane as an orifla plane bythe MOCVD method. Then, only TMG gas is stopped, a temperature is risento 1050° C. and, when a temperature reaches 1050° C., a nitridesemiconductor comprising undoped GaN is grown at a thickness of 2.5 μmusing TMG, ammonia and a silane gas as a raw material gas. On thenitride semiconductor, a protective membrane comprising SiO₂ is grown ata thickness of 0.5 μm by the CVD method, a stripe-like mask is formed,and etching is performed to form a protective membrane comprising SiO₂in which a stripe width is 14 μm and an interval between stripes is 6μm. This stripe-like protective membrane is in a direction vertical toan A plane of sapphire.

[0257] Then, a temperature is set at 1050° C., and a first nitridesemiconductor comprising GaN is grown at a thickness of 2 μm using TMG,ammonia, a silane gas and Cp₂Mg as a raw material gas under the reducedpressure condition by the MOCVD method. Upon this, a first nitridesemiconductor is grown starting at a part on which a SiO₂ protectivemembrane is not formed, and is grown transversely on this protectivemembrane. The growth is stopped before a first nitride semiconductorcompletely covers the SiO₂ protective membrane, and a distance betweenadjacent first nitride semiconductors is about 2 μm.

[0258] Then, the SiO₂ protective membrane is removed by 0.3 μm at atemperature of 120° C. using oxygen and CF₄ as an etching gas byisotropic etching which is dry etching.

[0259] Further, a second nitride semiconductor comprising GaN is grownat a thickness of 15 μm starting at a side and an upper plane of thetransversely grown first nitride semiconductor at a normal pressure anda temperature of 1050° C. using TMG, ammonia, a silane gas and Cp₂Mg asa raw material gas by the MOCVD method. A second nitride semiconductormay be grown under reduced pressure instead of normal pressure. On thethus obtained substrate, layers are grown until thick layer to p-sidecontact layer according to the same manner as that in the example 2 and,thereafter, each step is performed similarly to obtain a semiconductorlaser device of the present invention. In the thus obtainedsemiconductor laser device, continuous oscillation at an oscillationwavelength 405 nm is confirmed at room temperature and at a threshold2.0 kA/cm² and a high output 30 mW. In addition, in FFP, the better beamfree of ripple is obtained.

Example 4

[0260] In the example 1, before exposure of an n-type layer, removal byetching is performed so that an active layer in the vicinity of a lightemitting plane of a stripe-like convex part is left at a width of 2 μm,to form a shading layer forming plane and, further, a semiconductorlayer comprising GaN is laminated on this removed part to grow to thesame height as an upper plane of a p-contact layer. Thereafter, the sameprocedures as those in the example 1 are performed except that astripe-like convex part is formed corresponding to the left active layerhaving a width of 2 μm and an n-type layer is exposed, to obtain asemiconductor laser device of the present invention. In the resultingsemiconductor laser device, continuous oscillation at an oscillationwavelength 405 nm is confirmed at room temperature and at a threshold2.0 kA/cm² and a high output 30 mW. In addition, in FFP, the better beamfree of ripple and having a large light divergence angle is obtained.

Example 5

[0261] In the example 1, the same step for laminating a semiconductorlayer is performed, and steps after exposure of an n-type layer areperformed as follows: whereas an emitting plane is a cleavage plane inthe example 1, an emitting plane is formed by etching in an example 5.That is, as shown in FIG. 12, an emitting plane side end is at least nota single plane, but is a shape in which a difference in level is set.

[0262] (Exposure of an n-Type Layer and Formation of a Resonator Plane)

[0263] After a laminate structure is formed, a wafer is removed from areactor, a protective membrane comprising SiO₂ is formed on the surfaceof an uppermost layer p-type contact layer, and etching is performedwith SiCl₄ gas using RIE (reactive ion etching), to expose an n-typecontact layer on which an n-electrode is to be formed and, at the sametime, expose a plane which is to be a resonator plane. That is, althougha stripe-like convex part continues over a plurality of elements on awafer until final cleavage in the example 1, a plane orthogonal with astripe-like convex part is also etched upon exposure of an n-type layer,to form a resonator plane at the same time in the example 2. Upon this,a stripe-like convex part for two elements may continue.

[0264] (Formation of a Stripe-Like Convex Part and a Shading LayerForming Plane)

[0265] Then, in order to form a stripe-like waveguide, a protectivemembrane comprising SiO₂ is formed at a thickness of 0.5 μmapproximately on a front plane containing an uppermost layer p-typecontact layer and a resonator plane exposed in the previous step usingthe CVD apparatus and, thereafter, a mask having a prescribed shape isformed on a protective membrane, a stripe-like protective membrane isformed by the photolithography technique using a CF₄ gas in the RIEapparatus, and a stripe-like convex part is formed above an activelayer. A stripe-like convex part is formed orthogonal with a resonatorplane.

[0266] The vicinity of a resonator plane which is an end part of thisstripe-like convex part is further etched until an active layer isexposed, whereby, a second side and a non-resonator plane are formed.Upon this, they are formed in the vicinity of a resonator plane which isto be a light emitting side resonator plane, but may be formed on bothof them.

[0267] (Light Non-Transmittable Layer)

[0268] A shading layer continuing to a light non-resonator plane, asecond side and an exposed plane of an n-type layer is formed bysputtering while the aforementioned protective membrane is retained. Ashading layer comprises Si, and a thickness thereof is 5000 Å. Thisshading layer may be formed after a first insulating membrane is formedin a later step. Alternatively, it may be formed after an ohmicelectrode is formed, or after a second insulating membrane is formed.

[0269] (First Insulating Membrane)

[0270] A first insulating membrane comprising ZrO₂ is formed on thesurface of a p-type layer while a SiO₂ mask is retained. After formationof a first insulating membrane, it is soaked in a buffered solution,SiO₂ formed on an upper plane of a stripe-like convex part is dissolvedand removed, and ZrO₂ on a p-type contact layer is removed together withSiO₂ by a liftoff method. Thereby, a p-type layer is exposed on an upperplane of a stripe-like convex part, and a structure is obtained in whichfrom a side of a convex part to a p-type layer upper plane are coveredwith ZrO₂.

[0271] (Ohmic Electrode)

[0272] Then, a p-side ohmic electrode is formed on a p-type contactlayer. This ohmic electrode comprises Au—Ni, and is formed also over afirst insulating membrane on a p-type contact layer. In addition, anohmic electrode is formed also on an upper plane of an n-type contactlayer. An n-side ohmic electrode comprises Ti—Al, is parallel with astripe-like convex part, and is formed into a stripe having the sameextent of a length. After formation of them, they are annealed at 600°C. in the atmosphere at a ratio of oxygen:nitrogen of 80:20 to alloyp-side and n-side ohmic electrodes, and ohmic electrodes having thebetter ohmic properties are obtained.

[0273] (Second Insulating Membrane)

[0274] Then, a resist is coated on a part of a p-side ohmic electrodeand an n-side ohmic electrode on a stripe-like convex part and a secondinsulating membrane of a multi-layered membrane comprising SiO₂ and ZrO₂is formed on almost the whole plane except for a light emitting sideresonator plane. SiO₂ and ZrO₂ are alternately laminated at two pairs.And lifting off is conducted to expose a part of each electrode. Asecond insulating membrane is formed also on a shading layer. Further,since a second insulating membrane is formed so as to cover also a lightreflecting side resonator plane, this second insulating membranefunctions also as a light reflecting membrane (mirror). Like this, sinceat least one of resonator planes is formed by etching prior to aninsulating membrane forming step, a light reflecting membrane (mirror)can be formed so as to go behind in the wafer state before division.Thereby, a second insulating may be formed so that a material for alight emitting side resonator plane and a material for a lightreflecting side resonator plane are different or the second insulatingmembrane comprises reflecting membranes having a different thickness.

[0275] (Pad Electrode)

[0276] Then, a p-side pad electrode and an n-side pad electrode areformed so as to cover the aforementioned second insulating membrane.This pad electrode comprises Ni—Ti—Au, and is contacted with a p-sideohmic electrode and an n-side ohmic electrode, respectively, via asecond insulating membrane in a stripe-like manner. In addition, in thepresent example, as shown in FIG. 11, a p-side pad electrode 4 is formedalso on a stripe-like convex upper plane held by second sides via asecond insulating membrane.

[0277] (Division and Formation of a Light Emitting Side ProtectiveMembrane)

[0278] The previously exposed n-type layer is further etched until asubstrate is exposed. Thereby, only a substrate remains at a divisionposition and, as shown in FIG. 12, a resonator plane and an n-type layerend are formed by etching. Division into a bar is performed starting ata substrate side, in a direction vertical to a stripe-like electrode.Then, ZrO₂ is formed on a light emitting side, and SiO₂ is formed so asto cover it, to obtain a protective membrane. Finally, a bar is cut in adirection parallel with a stripe-like electrode to obtain asemiconductor laser device of the present invention. In this example, asshown in FIG. 12, an end of a substrate is protruded more than aresonator plane. However, since the protruded length can be suppressedsmall to an extent that a laser beam shape does not have no influence,there is no problem.

[0279] In the thus obtained semiconductor laser device, continuousoscillation at an oscillation wavelength 405 nm is confirmed at roomtemperature and at a threshold 2.0 kA/cm² and a high output 30 mW and,in addition, in FFP, the better beam free of ripple is obtained.

Example 6

[0280] In the example 4, the same procedures as those in the example 4are performed except that Ti is used as a shading layer and SiO₂ is usedas an insulating membrane, to obtain a semiconductor laser device of thepresent invention. First, after SiO₂ is formed, Ti is formed, whereby, ashading layer is obtained which is excellent in the insulating propertyand which can effectively block stray light. A thickness of Ti is 4500Å, and a thickness of SiO₂ is 1500 Å. In the resulting semiconductorlaser device, continuous oscillation at an oscillation wavelength 405 nmis confirmed at room temperature and at a threshold 2.0 kA/cm² and ahigh output 30 mW and in addition, in FFP, the better beam free ofripple and having the large light divergence angle is obtained.

Example 7

[0281] According to the same manner as that in the example 6 except thata substrate having the same nitride semiconductor as that in the example3 is used, a semiconductor laser device of the present invention isobtained. In the resulting semiconductor laser device, continuousoscillation at an oscillation wavelength 405 nm is confirmed at roomtemperature and at a threshold 2.0 kA/cm² and a high output 30 mW and inaddition, FFP, the better beam free of ripple is obtained.

Example 8

[0282] A semiconductor laser device of an example 8 is preparedaccording to the same manner as that in the example 1 except that alight-transmitting membrane 9 a is formed under the shading layer 9 in asemiconductor laser device of the example 1 as described below (FIG.13A-FIG. 13C).

(Light-Transmitting Membrane 9 a)

[0283] According to the same manner as that in the example 1, afterformation of a stripe-like convex part and a shading membrane formingplane, a light-transmitting membrane continuing to a light non-resonatorplane, a second side and an exposed plane of an n-type layer is formedby sputtering while a protective membrane used for the above formationis retained. A light-transmitting membrane comprises Rh oxide, and athickness thereof is 500 Å.

[0284] (Shading Membrane)

[0285] Further, a shading membrane is formed on the aforementionedlight-transmitting membrane. This shading membrane, like alight-transmitting membrane, comprises Rh oxide, and a thickness thereofis 1500 Å. This shading membrane can be formed by changing a constituentratio of Rh and that of oxygen by reducing the vacuum degree, in thesputtering conditions for forming the aforementioned light-transmittingmembrane. A layer having the different membraneous properties,particularly the light transmittance can be formed by changing only thevacuum degree while an apparatus is not changed. Theselight-transmitting membranes and shading membrane may be formed after afirst insulating membrane is formed in a later step. Alternatively, theymay be formed after formation of an ohmic electrode and formation of asecond insulating membrane.

[0286] According to the same manner as that in the example 1 regardingfrom formation of a first insulating membrane to formation of a mirror,a semiconductor laser device is manufactured.

[0287] In the thus obtained semiconductor laser device, continuousoscillation at an oscillation wavelength 405 nm was confirmed at roomtemperature and at a threshold 2.0 kA/cm² and a high output 30 mW and,in addition, in FFP, the better beam free of ripple was obtained.

Example 9

[0288] In the semiconductor laser device in an example 9, afterlamination is performed up to a p-side contact layer as in the laserdevice in the same manner as in the example 2, a plane for forming ashading membrane and a light-transmitting membrane, a light-transmittingmembrane and a shading membrane are formed as follows.

[0289] (Formation of a Shading Membrane and Light-Transmitting MembraneForming Plane)

[0290] After lamination up to a p-side contact layer and exposure of ann-type layer, a stripe-like convex part (ridge) having a width of 1.6 μmis formed. Then, a mask having a larger width of that of a ridge isprovided in the vicinity of a resonating end on an emitting side forforming a light-transmitting membrane, and etching is performed until ann-type layer, whereby, a second side on a plane different from a ridgeside is formed. Although a width of an active layer can be controlled bya mask having a larger width of that of this ridge, as in FIG. 13A, inorder to remove only an active layer in the vicinity of an emitting sideresonator plane, a mask is provided on an almost whole plane other thanthe vicinity of a resonator plane, and a mask having a larger width ofthat of a ridge is provided in the vicinity of a resonator plane,whereby, a structure can be obtained in which an active layer is removedin a limited part, that is, in the vicinity of a resonator plane. Inaddition, a mask having a width of that of a ridge may be provided overthe whole ridge. Here, a resonator plane in which a width of an activelayer of a resonator plane of an emitting plane is about 7 μm is formedby providing a mask at a width of about 7 μm so that a ridge isapproximately at a center thereof and etching up to an n-type layer nearan active layer. The thus formed etching planes are a non-resonatorplane and a second side and, on both, a light-transmitting membrane anda shading membrane are provided.

[0291] (Light-Transmitting Membrane and Shading Membrane)

[0292] A light-transmitting membrane is formed on the thus formed secondside and non-resonator plane, and an exposed plane of an n-type layer bysputtering. First, Rh oxide is formed at a thickness of 500 Å as a lowerlight-transmitting membrane, the same Rh oxide as that for alight-transmitting membrane is formed thereon at a thickness of 500 Å asan intermediate layer by changing the sputtering conditions, and thesame Rh oxide is further formed thereon at a thickness of 1500 Å as anupper shading membrane by changing the sputtering conditions. In thesputtering conditions, a three-layered structure may be obtained byforming a lower light-transmitting membrane, an intermediate membraneand an upper shading membrane under the constant conditions, or alight-transmitting membrane and a shading membrane are formed under theconstant conditions and only an intermediate membrane is formed byreducing the vacuum degree gradually. Accordingly, Rh oxides having thedifferent constituent ratio can be easily formed. Although in theexample 2, since a mask used for forming a light-transmitting membraneforming plane is used as it is, a light-transmitting membrane and ashading membrane are formed on a second side, a non-resonator plane, andan exposed plane of an n-type layer, there is no problem even when amask is provided so as to extend until the surface of a p-type layer. Byformation of a light-transmitting membrane and a shading membrane untila part of the surface (upper plane) of a p-type layer, leakage of thelight toward an upper direction can be also prevented. In addition,although peeling easily occurs in some cases by formation of an end partof a shading membrane at an edge between an end and an upper plane, ashading membrane can be formed with the better tightness and the stablebeam properties can be obtained by providing so as to also continue toan upper plane like this.

[0293] Thereafter, according to the same manner as that for the example2, the semiconductor laser device of the example 9 is manufactured.

[0294] In the thus obtained semiconductor laser device of the example 9,continuous oscillation at an oscillation wavelength 405 is confirmed atroom temperature and a threshold 2.0 kA/cm² and a high output 30 mW and,in addition, in FFP, the better beam free of repple can be obtained.

Example 10

[0295] According to the same manner as that for the example 9 exceptthat a substrate prepared as in the example 3 is used, a semiconductorlaser device is manufactured.

[0296] The thus manufactured laser device of an example 10 has thesimilar properties to those of the semiconductor laser device of theexample 3.

Example 11

[0297] In the example 9, the same step of laminating semiconductorlayers is performed, and steps after exposure of an n-type layer areperformed as follows: In contrary to the example 9 in which an emittingplane is a cleavage plane, an emitting plane is formed by etching in theexample 11. That is, an emitting plane side end shown in FIG. 12 is nota single plane, but a shape in which a difference in level is set. Thecase where an emitting plane is formed by such the etching is effectivewhen a substrate which is difficult to be cleaved is used.

[0298] (Exposure of an n-Type Layer and Formation of Resonator Plane)

[0299] After formation of a laminate structure, a wafer is removed froma reactor, a protective membrane comprising SiO₂ is formed on thesurface of an uppermost p-type contact layer, which is etched with aSiCl₄ gas using RIE (reactive ion etching), and an n-type contact layeron which an n-electrode is to be formed and, at the same time, a planewhich is to be a resonator plane are exposed. That is, in the example 9,a stripe-like convex part continues over a plurality of elements on awafer until final cleavage, whereas in the example 4, a plane orthogonalwith a stripe-like convex part is also etched upon exposure of an n-typelayer, and a resonator plane is formed at the same time. Upon this, astripe-like convex part corresponding to two elements may be continuous.

[0300] (Formation of a Stripe-Like Convex Part and a Shading LayerForming Plane)

[0301] Then, in order to form a stripe-like waveguide, after aprotective membrane comprising SiO₂ is formed at a thickness of 0.5 μmon an almost whole front plane containing an uppermost p-type contactlayer and a resonator plane exposed in the previous step using a CVDapparatus, a mask having a prescribed shape is provided on a protectivemembrane, a stripe-like protective membrane is formed by etching using aCHF₃ gas in RIE apparatus, and whereby, a stripe-like convex part isformed above an active layer. A stripe-like convex part is formedorthogonal with a resonator plane.

[0302] By further etching the vicinity of a resonator plane which is anend of this stripe-like convex part until an active layer is exposed, asecond side and a non-resonator plane are formed. Upon this, they areformed in the vicinity of a resonator plane which is to be a lightemitting side resonator plane, but they may be formed on both of them.

[0303] (Light-Transmitting Membrane and Shading Membrane)

[0304] A light-transmitting membrane and a shading membrane continuingto a light non-resonator plane, a second side and an exposed plane of ann-type layer are formed by sputtering while the aforementionedprotective membrane is retained. As a light-transmitting membrane, Rhoxide is formed at a thickness of 600 Å, the same Rh oxide is formedthereon at a thickness of 600 Å by changing the sputtering conditions,and the same Rh oxide is further formed thereon at a thickness of 2000 Åby changing the sputtering conditions. Each layer is formed under theconstant sputtering conditions, and the vacuum degree is reduced at anupper layer. Whereby, Rh oxides having the different constituent ratiocan be easily formed. Those light-transmitting membrane and shadingmembrane may be formed after a first insulating membrane is formed in apost-step. Further, they may be formed after an ohmic electrode isformed, or after a second insulating membrane is formed.

[0305] (First Insulating Membrane)

[0306] A first insulating membrane comprising ZrO₂ is formed on thesurface of a p-type layer while the SiO₂ mask is retained. The formedfirst insulating membrane is soaked in a buffered solution to dissolveand remove SiO₂ formed on an upper plane of a stripe-like convex part,and ZrO₂ on a p-type contact layer is removed together with SiO₂ by aliftoff method. Whereby, a p-type layer is exposed on an upper plane ofa stripe-like convex part, leading to a structure in which from a sideof a convex part to an upper plane of a p-type layer are covered withZrO₂.

[0307] (Ohmic Electrode)

[0308] Then, a p-side ohmic electrode is formed on a p-type contactlayer. This ohmic electrode comprises Au—Ni, and is formed also over afirst insulating membrane on a p-type contact layer. In addition, anohmic electrode is formed also on an upper plane of an n-type contactlayer. An n-side ohmic electrode comprises Ti—Al, is parallel with astripe-like convex part, and is formed into stripes having an equivalentextent of a length. After formation of them, p-side and n-side ohmicelectrodes are alloyed by annealing at 600° C. in the atmosphere at aratio of oxygen:nitrogen of 80:20, and an ohmic electrode having thebetter ohmic properties is obtained.

[0309] (Second Insulating Membrane)

[0310] Then, a second insulating membrane of a multi-layered membranecomprising SiO₂ and TiO₂ is formed on an almost whole plane except for alight emitting side resonator plane. SiO₂ and TiO₂ are alternatelylaminated at two pairs. A resist is coated on a part of a p-side ohmicelectrode and an n-side ohmic electrode on a stripe-like convex part,which is dry-etched to expose a part of each electrode. A secondinsulating membrane is formed also on an upper plane of a shading layer.Since a second insulating membrane is further formed so as to cover alight reflecting side resonator plane, this second insulating membranefunctions also as a light reflecting membrane (mirror). Like this, sinceat least one resonator plane is formed by etching prior to an insulatingmembrane forming step, a second insulating membrane can be formed so asto go behind in the wafer state before division of a light reflectingmembrane (mirror). Thereby, a second insulating membrane may be formedof a material for a light emitting side resonator plane and a materialfor a light reflecting side resonator plane may be different, or ananti-reflection membrane comprising materials having a differentthickness.

[0311] (Pad Electrode)

[0312] Then, a p-side pad electrode and an n-side pad electrode areformed so as to cover the aforementioned second insulating membrane.This pad electrode comprises Ni—Ti—Au, and is contacted with a p-sideohmic electrode and an n-side ohmic electrode, respectively, via asecond insulating membrane. In addition, a pad electrode is formed alsoon an upper plane of a stripe-like convex part held by second sides.

[0313] (Division and Formation of a Light Emitting Side Mirror)

[0314] The previously exposed n-type layer is further etched until asubstrate is exposed. Therefore, only a substrate is left at a divisionposition, and a resonator plane and an n-type layer end are formed byetching, which is divided into a bar starting at a substrate side in adirection vertical to a stripe-like electrode. Then, SiO₂ is formed on alight emitting side resonator plane, and ZrO₂ is formed so as to coverit to obtain a mirror. Finally, a bar is cut in a direction parallelwith a stripe-like electrode to obtain a semiconductor laser device ofthe present invention.

[0315] In the thus obtained semiconductor laser device of the example11, continuous oscillation at an oscillation wavelength 405 nm isconfirmed at room temperature and at a threshold 2.0 kA/cm² and a highoutput 30 mW and, in addition, in FFP, the better beam free of ripple isobtained.

Example 12

[0316] In the semiconductor laser device of an example 12, according tothe same manner as that in the example 1, a buffer layer and a groundlayer are grown on a substrate, and an n-type contact layer comprisingAlGaN doped with Si at 1×10¹⁸/cm³ is grown on the ground layer (nitridesemiconductor substrate) at a thickness of 4.5 μm at 1050° C. using TMG,TMA and anmmonia, and a silane gas as an impurity gas.

[0317] Then, according to the same manner as that in the example 1, acrack preventing layer, an n-type cladding layer, an n-light guidinglayer, an active layer, a p-type cap layer, a p-type light guidinglayer, a p-type cladding layer and a p-type contact layer are grown onthe n-type contact layer comprising AlGaN. Further, according to thesame manner as that in the example 1, an n-type layer is exposed, aresonator plane is formed, and a convex part is formed as describedbelow.

[0318] (Formation of a Stripe-Like Convex Part)

[0319] In the present the example 12, in order to form a stripe-likewaveguide region, after a protective membrane comprising Si oxide(mainly SiO₂) is formed on an almost whole plane of an uppermost p-typecontact layer at a thickness of 0.5 μm by the CVD apparatus, a maskhaving a prescribed shape is provided on a protective membrane, and astripe-like protective membrane is formed by the photolithographytechnique using a CF₄ gas in the RIE apparatus, whereby, a stripe-likeconvex part is formed above an active layer. Alternatively, in the RIEapparatus, CHF₃ can be used instead of a CF₄ gas.

[0320] After formation of a convex part, according to the same manner asthat in the example 1, a first insulating membrane and p-side and n-sideohmic electrodes are formed, and the following steps are performed tomanufacture a semiconductor laser device.

[0321] (Second Insulating Membrane)

[0322] Then, a resist is coated on a part of a p-side ohmic electrodeand an n-side ohmic electrode on a stripe-like convex part, a secondinsulating membrane comprising Si oxide (mainly SiO₂) is formed on awhole plane except for a division position, and liftoff is performed toexpose a part of a p-side ohmic electrode and an n-side ohmic electrode.

[0323] (Pad Electrode)

[0324] Then, a p-side pad electrode and an n-side pad electrode areformed, respectively, so as to contact with a p-side ohmic electrode andan n-side ohmic electrode via an opening of the aforementioned secondinsulating membrane. Electrodes comprise Ni—Ti—Au. This pad electrode iscontacted with an exposed ohmic electrode in a stripe-like manner.

[0325] (Exposure of a Substrate)

[0326] Then, after SiO₂ is formed on a front plane of a wafer, a resistmembrane is formed thereon except for an exposed plane of an n-typecontact layer, and etched until a substrate is exposed. Since a resistmembrane is formed also on a side such as a resonator plane, afteretching, an end is formed which includes two steps of a side such as thepreviously formed resonator plane (including a p-type layer, an activelayer, and a part of an n-type layer), and an n-type layer between aresonator plane and a substrate.

[0327] (Second Protective Membrane)

[0328] Then, a second protective membrane is formed. A light emittingside resonator plane is masked with a resist membrane and the like, anda second protective membrane comprising SiO₂ (1350 Å)/Ti (2250 Å) isformed by sputtering. The transmittance of this second protectivemembrane is about 0.01% and, thus, the shading effect of approximately100% is obtained.

[0329] (Bar-Like Division)

[0330] After formation of a p-side ohmic electrode and an n-side ohmicelectrode as described above, a substrate is abraded to a totalthickness including a substrate of 200 μm, and a back metal comprisingTi—Pt—Au is formed on a back, which is divided into a bar starting at asubstrate side in a direction vertical to a stripe-like electrode. Uponthis, when a scribe is provided, corresponding to a division positionfrom a backside of a substrate before bar-like division, the divisionbecomes easy in a later step.

[0331] (Light Reflection Side Mirror and First Protective Membrane)

[0332] In the semiconductor thus divided into a bar, a light emittingside resonator plane is arrayed on one side of a bar, and a lightreflecting side resonator plane is arrayed on an opposite side. An angleof a few such the bars is changed so that a light emitting sideresonator plane and a light reflecting side resonator plane face thesame direction. Then, film formation jigs are arrayed between respectivebars via a spacer without a gap. By provision of a spacer like this, aprotective membrane is not formed on an electrode and the like formed ina device. First, ZrO₂ and 6 pairs of (SiO₂/ZrO₂) are formed on a lightreflecting side resonator plane to obtain a mirror. Then, on a lightemitting side, a membrane of Nb₂O₅ as a first protective membrane isformed at a thickness of 400 Å. This Nb₂O₅ is provided over a lightemitting plane of a resonator plane and a second protective membraneprovided in the vicinity of the light emitting plane.

[0333] Additionally, the light transmittance of the second protectivemembrane comprising Nb₂O₅ is about 82%.

[0334] Finally, a bar is cut in a direction parallel with a stripe-likeconvex part to obtain a semiconductor laser device of the presentinvention.

[0335] In the thus obtained semiconductor laser device, continuousoscillation at an oscillation wavelength 405 nm was confirmed at roomtemperature and at a threshold 2.0 kA/cm² and a high output 30 mW and,in addition, in FFP, the better beam free of ripple was obtained.

Example 13

[0336] In an example 13, using a nitride semiconductor substratecomposed of GaN formed on sapphire as a substrate (manufacturedaccording to the same manner as that in the example 2), a semiconductorlaser device shown in FIG. 17 is manufactured.

[0337] Specifically, the semiconductor laser device is manufactured asdescribed below.

[0338] (Buffer Layer)

[0339] First, a buffer layer composed of undoped AlGaN having an Alcrystal mixing ratio of 0.01 is formed on a ground layer of a nitridesemiconductor substrate. This buffer layer can be omitted. However, whena substrate using transverse growth is GaN, or when a ground layerformed by transverse growth is GaN, a pit can be reduced by using abuffer layer composed of a nitride semiconductor having a smallerthermal expansion coefficient, that is, AlaGa1−aN (0<a≦1) or the likeand, therefore, it is preferable to form a buffer layer. That is, like aground layer, when another nitride semiconductor is grown on a nitridesemiconductor layer which is formed accompanied with transverse growth,a pit easily occurs, but this buffer layer has the effect of preventingoccurrence of a pit.

[0340] It is preferable that an Al crystal mixing ratio of a bufferlayer is 0<a<0.3, whereby, a buffer layer having the bettercrystallinity can be formed. In addition, this buffer layer may beformed as a layer also having the function as an n-side contact layer,or after formation of a buffer layer, an n-side contact layer having thesame composition as that of the aforementioned buffer layer may beformed to impart the buffer effect to the n-side contact layer. That is,this buffer layer can reduce a pit to improve the device properties byprovision between a transversely grown layer (GaN substrate) and anitride semiconductor layer constituting a device structure, or anactive layer in a device structure and a transversely grown layer (GaNsubstrate), more preferably provision of at least one layer on asubstrate side in a device structure, or between a lower cladding layerand a transversely grown layer (GaN substrate). In addition, a bufferlayer also having the function as an n-side contact layer is intended,it is preferable that an Al crystal mixing ratio a is 0.1 or less sothat the better ohmic contact with an electrode is obtained. A bufferlayer to be formed on this ground layer may be grown at a lowtemperature of not lower than 300° C. and not higher than 900° C. like abuffer layer to be provided on the aforementioned heterogeneoussubstrate, but when it is preferably single crystal-grown at atemperature of not lower than 800° C. and not higher than 1200° C.,there is a tendency that the aforementioned pit reducing effect can beeffectively obtained. Further, this buffer layer may be doped with ann-type or p-type impurity, or may be undoped, but in order to obtain thebetter crystallinity, the buffer layer is preferably formed undoped.Still further, when two or more layers of buffer layer are provided,they may be provided by changing the n-type or p-type impurityconcentration and an Al crystal mixing ratio.

[0341] (N-Type Contact Layer)

[0342] An n-side contact layer composed of Al_(0.01)Ga_(0.99)N dopedwith Si at 3×10¹⁸/cm³ is formed on a buffer layer at a thickness of 4μm.

[0343] (Crack Preventing Layer)

[0344] A crack preventing layer composed of In_(0.06)Ga_(0.94)N isformed on an n-side contact layer at a thickness of 0.15 μm.

[0345] (N-Side Cladding Layer)

[0346] An n-side cladding layer of a superlattice structure having atotal thickness of 1.2 μm is formed on a crack preventing layer.

[0347] Specifically, an n-side cladding layer is formed by alternatelylaminating an undoped Al_(0.05)Ga_(0.95)N layer having a thickness of 25A and a GaN layer doped with Si at 1×10¹⁹/cm³ having a thickness of 25A.

[0348] (N-Side Light Guiding Layer)

[0349] An n-side light guiding layer composed of undoped GaN having athickness of 0.15 μm is formed on an n-side cladding layer.

[0350] (Active Layer)

[0351] An active layer of a multiple quantum well structure having atotal thickness of 550 Å is formed on an n-side light guiding layer.

[0352] Specifically, an active layer is formed by laminating a barrierlayer (B) composed of Si-doped In_(0.05)Ga_(0.95)N doped with Si at5×10¹⁸/cm³ having a thickness of 140 Å and a well layer (W) composed ofundoped In_(0.13)Ga_(0.87)N having a thickness of 50 Å in an order of(B)-(W)-(B)-(W)-(B).

[0353] (P-Side Electron Confining Layer)

[0354] A p-side electron confining layer composed of p-typeAl_(0,3)Ga_(0.7)N doped with Mg at 1×10²⁰/cm³ having a thickness of 100Å is formed on an active layer.

[0355] (P-Side Light Guiding Layer)

[0356] A p-side light guiding layer composed of p-type GaN doped with Mgat 1×10¹⁸/cm³ having a thickness of 0.15 μm is formed on a p-sideelectron confining layer.

[0357] (P-Side Cladding Layer)

[0358] A p-side cladding layer of a superlattice structure having atotal thickness of 0.45 μm is formed on a p-side light guiding layer.

[0359] Specifically, a p-side cladding layer is formed by alternatelylaminating undoped Al_(0.05)Ga_(0.95)N having a thickness of 25 A andp-type GaN doped with Mg at 1×10²⁰/cm³ having a thickness of 25 A.

[0360] (P-Side Contact Layer)

[0361] A p-side contact layer composed of p-type GaN doped with Mg at2×10²⁰/cm³ having a thickness of 150 Å is formed on a p-side claddinglayer.

[0362] (Exposure of an n-Type Layer and Formation of a Stripe-LikeConvex Part)

[0363] After a device structure from an n-side contact layer to a p-sidecontact layer is formed as described above, according to the same manneras that in the example 12, after an n-type contact layer is exposed, astripe-like convex part (ridge) is formed by etching.

(Formation of a Second Side and a Non-Resonator Plane)

[0364] Then, a second side on which a second protective membrane is tobe formed and a non-resonator plane are formed. A second side and anon-resonator plane are formed by forming a mask on parts other than anend in the vicinity of a resonator plane and performing etching. Here,since a second side is formed so as to be nearer an end of a device thana ridge side, as shown in FIG. 17, a width of an active layer is largerthan a width of a ridge in an end in a direction vertical to a ridge.

[0365] (Second Protective Membrane)

[0366] Then, a second protective membrane is formed on the second sideand the non-resonator plane formed as described above. A multi-layeredmembrane composed of SiO₂/Ti as a second protective membrane is formedby sputtering using the aforementioned mask as it is.

[0367] (First Insulating Membrane to Second Insulating Membrane)

[0368] Then, as in the example 12, a first insulating membrane composedof ZrO₂, an ohmic electrode, and a second insulating membrane composedof SiO₂/TiO₂ are formed.

[0369] (Pad Electrode)

[0370] Then, RhO—Pt—Au is formed as a p-side pad electrode and Ni—Ti—Auis formed as an n-side pad electrode.

[0371] (Peeling of a Heterogeneous Substrate)

[0372] Subsequently, only a thick layer is left (conversion into singlebody) by removing a sapphire substrate, a low temperature-grown bufferlayer, a ground layer and a part of a thick layer to adjust a thicknessof a GaN substrate to 80 μm. Here, although as a thick layer accordingto HVPE, other nitride semiconductors may be used besides GaN, in thepresent invention, it is preferable to use GaN or AlN which has thebetter crystallinity and on which a thick nitride semiconductor can beeasily grown. In addition, in removal of a heterogeneous substrate andthe like, a part of a thick layer may be removed prior to formation ofthe aforementioned device structure, or removal may be performed at anystage after formation of a waveguide, or after formation of anelectrode. In addition, by removing a heterogeneous substrate and thelike prior to cutting of a wafer into a bar and a chip, cutting andcleavage can be performed using a cleavage plane of a nitridesemiconductor (hexagonal crystal system-approximated {11-00} M plane,{1010} A plane, (0001) C plane) upon cutting into a chip.

[0373] (Formation of a Resonator Plane)

[0374] Then, a eutectic crystal metal composed of Ti—Pt—Au is formed ona back, which is divided into a bar-like starting at a substrate side ina direction vertical to a stripe-like electrode to form a resonatorplane according to the same manner as that in the example 1.

[0375] (Light Reflecting Side Mirror and First Protective Membrane)

[0376] Then, a mirror composed of six pairs of ZrO₂ and (SiO₂/ZrO₂) isformed on a light reflecting side resonator plane, and a membrane ofNb₂O₅ as a first protective membrane is formed on a light emitting side.This Nb₂O₅ is provided on a light emitting side resonator plane and on asecond protective membrane provided in the vicinity of a resonatorplane. Further, the bar is cleaved on an A plane vertical to an M planecleaved between respective devices parallel with a resonator directionto obtain a laser chip.

[0377] The thus obtained laser device has a threshold current density of2.5 kA/cm², a threshold voltage of 4.5V, an oscillation wavelength of405 nm and an aspect ratio of an emitted laser beam of 1.5 at roomtemperature. In addition, a high output laser device of 30 mW continuousoscillation having a long life of 1000 hours or longer can be obtained.In addition, the present laser device can oscillate continuously at anoutput region of 5 mW to 80 mW and, in the output region, has the beamproperties suitable as a light source for an optical disc system.

Example 14

[0378] According to the same manner as that in the example 12 exceptthat steps are changed as described below, a semiconductor emittingdevice as shown in FIG. 18 is obtained.

[0379] [Exposure of an n-Type Layer]

[0380] An n-type layer is exposed as in the example 12 and, upon this, aresonator plane is made not to be formed.

[0381] (Formation of a Stripe-Like Convex Part, and Formation of aNon-Resonator Plane and a Second Side)

[0382] After formation of a stripe-like convex part, a side of astripe-like convex part in the vicinity of a device division plane isfurther etched until an active layer using the same mask to remove acorner part of a device as shown in FIG. 5, whereby, a non-resonatorplane and a second side are formed. On this plane, a second protectivemembrane is formed. ZrO₂/RhO is used as a second protective membrane.

[0383] (Division and Formation of a Resonator Plane)

[0384] Prior to formation of an emitting side mirror, a sapphiresubstrate of a wafer is abraded to 70 μm, which is cleaved in a bar-likestarting at a substrate side in a direction vertical to a stripe-likeelectrode, to obtain a cleavage plane (11-00 plane, plane correspondingto a side of a hexagonal pillar crystal=M plane), whereby, a resonatorplane is formed. Then, a first protective membrane is provided on aresonator plane on an emitting side of a resonator plane. Nb₂O₅ is usedas a first protective membrane.

[0385] In the thus obtained semiconductor laser device, continuousoscillation at an oscillation wavelength 405 nm is confirmed at roomtemperature and at a threshold 2.0 kA/cm² and a high output 30 mW, inaddition, the better beam having a wider divergence angle than that inthe example and free of ripple in FFP is obtained.

[0386] Industrial Applicability

[0387] As explained above, a semiconductor laser device having betterfar field pattern (FFP) is provided and it can be utilized in variousequipment such as an electronic equipment such as DVD, a medicalequipment, a processing equipment and a light source for an opticalfiber communication.

1. A semiconductor laser device comprising a laminate structure in whicha first conductive type semiconductor layer, an active layer and asecond conductive type semiconductor layer different from the firstconductive type are laminated in this order, said laminate structurehaving a waveguide region to guide a light in one direction andresonator planes for laser oscillation on both ends, characterized inthat said laminate structure has a non-resonator plane which isdifferent from the resonator plane on one end side, said non-resonatorplain being formed so as to contain a cross-section of said active layerand said cross-section of said active layer of the non-resonator planeis covered with a shading layer.
 2. The semiconductor laser deviceaccording to claim 1; wherein said resonator plane is projected morethan said non-resonator plane.
 3. The semiconductor laser deviceaccording to claims 1 or 2; wherein said resonator plane is a lightemitting plane.
 4. A semiconductor laser device comprising a laminatestructure in which a first conductive type semiconductor layer, anactive layer and a second conductive type semiconductor layer differentfrom the first conductive type are laminated in this order, saidlaminate structure having a waveguide region to guide a light in onedirection and resonator planes for laser oscillation on both ends,characterized in that a side of said laminate structure has a first sidecontaining a cross-section of said active layer, and a second side whichis situated nearer said waveguide region than the first side andcontains a cross-section of said active layer, and a shading layer isprovided on said cross-section of said active layer of the second side.5. The semiconductor laser device according to claim 4; wherein saidsecond side is provided in the vicinity of a light emitting plane.
 6. Asemiconductor laser device comprising a laminate structure in which afirst conductive type semiconductor layer, an active layer and a secondconductive type semiconductor layer different from the first conductivetype are laminated in this order, said laminate structure having awaveguide region to guide a light in one direction and resonator planesfor laser oscillation on both ends, characterized in that said laminatestructure has a non-resonator plane which is different from saidresonator plane on, said non-resonator plain being formed so as tocontain a cross-section of said active layer, and a side of saidlaminate structure has a first side containing a cross-section of saidactive layer, and a second side which is situated nearer said waveguideregion than the first side and near the emitting plane, and whichcontains a cross-section of an active layer, and a shading layer isprovided on said cross-section of said active layer of at least one ofsaid non-resonator plane and said second side.
 7. The semiconductorlaser device according to claim 6; wherein said non-resonator plane andsaid second side are continuously connected.
 8. The semiconductor laserdevice as in any one of claims 1-7; wherein a stripe-like convex part isformed on said laminate structure so as to form said waveguide region.9. The semiconductor laser device as in any one of claims 1-8; whereinsaid shading layer is formed in contact with said laminate structure.10. The semiconductor laser device as in any one of claims 1-8; whereinan insulating layer is formed between said shading layer and saidlaminate structure.
 11. The semiconductor laser device as in any one ofclaims 1-10; wherein said shading layer is made of one selected from thegroup consisting of a conductor, a semiconductor and an insulator. 12.The semiconductor laser device according to claim 11; wherein saidshading layer is a dielectric multi-layered membrane.
 13. Thesemiconductor laser device as in any one of claims 1-12; wherein saidfirst conductive type semiconductor layer, said active layer and saidsecond conductive type semiconductor layer are made of a nitridesemiconductor.
 14. The semiconductor laser device according to claim 13;wherein said first conductive type semiconductor layer has an n-typenitride semiconductor and said second conductive type semiconductorlayer has a p-type nitride semiconductor.
 15. The semiconductor laserdevice according to claim 13; wherein said shading layer is made of Tiand said insulating layer made of SiO₂.
 16. The semiconductor laserdevice as in any one of claims 1-14; wherein said shading layercomprises an Rh oxide.
 17. The semiconductor laser device as in any oneof claims 1-16; wherein said shading layer is a multi-layered membranecomposed of layers which comprise the same material and have a differentconstitutional ratio.
 18. A semiconductor laser device comprising alaminate structure in which a first conductive type semiconductor layer,an active layer and a second conductive type semiconductor layerdifferent from the first conductive type are laminated in this order,said laminate structure having a waveguide region to guide a light inone direction, characterized in that said laminate structure has ashading membrane provided in the vicinity of an emitting part of one endand at least one layer of a light transmittable membrane comprising thesame elements as those constituting the shading membrane and having thehigher transmittance than that of a shading membrane, said lighttransmittable membrane being provided between the shading membrane andthe laminate structure.
 19. The semiconductor laser device according toclaim 18; wherein said shading membrane and said light transmittablemembrane contain at least an Rh oxide.
 20. A semiconductor laser devicecomprising a laminate structure in which a first conductive typesemiconductor layer, an active layer and a second conductive typesemiconductor layer different from the first conductive type arelaminated in this order, said laminate structure having a waveguideregion to guide a light in one direction, characterized in that saidlaminate structure has a protective membrane on at least one end facewhich has a first protective membrane and a second protective membranehaving the lower light transmittance than that of the first protectivemembrane.
 21. The semiconductor laser device according to claim 20;wherein said first protective membrane is provided on an emitting partof an emitting plane, and-the second protective membrane is provided inthe vicinity of the emitting part.
 22. The semiconductor laser deviceaccording to claims 20 or 21; wherein both of the first protectivemembrane and the second protective membrane are formed on the same endface.
 23. The semiconductor laser device as in any one of claims 20-22;wherein said emitting plane is formed so as to be projected.
 24. Thesemiconductor laser device as in any one of claims 20-23; wherein thefirst protective membrane is a single-layered or a multi-layeredmembrane of at least one selected from compounds such as oxides,nitrides and fluorides of Si, Mg, Al, Hf, Nb, Zr, Sc, Ta, Ga, Zn, Y, Band Ti.
 25. The semiconductor laser device as in any one of claims20-24; wherein the first protective membrane is an anti-reflectionmembrane.
 26. The semiconductor laser device as in any one of claims20-25; wherein the first protective membrane has a refractive indexwhich is within ±10% of that of said laminate structure.
 27. Thesemiconductor laser device as in any one of claims 20-26; wherein thesecond protective membrane is a shading membrane.
 28. The semiconductorlaser device as in any one of claims 20-27; wherein the first protectivemembrane is Nb₂O₅ and the second protective membrane is a shadingmembrane.
 29. The semiconductor laser device as in any one of claims20-28; wherein said first conductive type semiconductor layer, saidactive layer and said second conductive type semiconductor layer aremade of a nitride semiconductor.
 30. The semiconductor laser deviceaccording to claims 29; wherein said first conductive type semiconductorlayer has an n-type nitride semiconductor, and said second conductivetype semiconductor layer has a p-type nitride semiconductor.